diff --git a/src/ApiResource/Version.php b/src/ApiResource/Version.php
index f37b79e..103e649 100644
--- a/src/ApiResource/Version.php
+++ b/src/ApiResource/Version.php
@@ -3,10 +3,10 @@
 namespace App\ApiResource;
 
 use ApiPlatform\Metadata as API;
-use App\Filter\VersionResourceFilter;
-use App\Filter\VersionResourceIdFilter;
+use App\Filter\ResourceVersionResourceFilter;
+use App\Filter\ResourceVersionResourceIdFilter;
 use App\Service\ApiResourceNormalizer;
-use App\State\VersionStateProvider;
+use App\State\ResourceVersionStateProvider;
 use Gedmo\Loggable\Entity\LogEntry;
 
 /**
@@ -15,10 +15,10 @@ use Gedmo\Loggable\Entity\LogEntry;
  * This allows us to keep track of the flow and the evolution of records in the platform.
  * Looking at the changes done between one version and the next one we can reconstruct how a resource was at a certain point in time.
  */
-#[API\ApiFilter(VersionResourceFilter::class, properties: ['resource'])]
-#[API\ApiFilter(VersionResourceIdFilter::class, properties: ['resourceId'])]
-#[API\GetCollection(provider: VersionStateProvider::class)]
-#[API\Get(provider: VersionStateProvider::class)]
+#[API\ApiFilter(ResourceVersionResourceFilter::class, properties: ['resource'])]
+#[API\ApiFilter(ResourceVersionResourceIdFilter::class, properties: ['resourceId'])]
+#[API\GetCollection(provider: ResourceVersionStateProvider::class)]
+#[API\Get(provider: ResourceVersionStateProvider::class)]
 class Version
 {
     public function __construct(
@@ -67,21 +67,6 @@ class Version
         return $this->log->getObjectId();
     }
 
-    /**
-     * The full resource data, reconstructed from the current resource data merged with versioned data.
-     */
-    public function getResourceData()
-    {
-        $entity = $this->entity;
-
-        foreach ($this->log->getData() as $changedProperty => $changedValue) {
-            $setter = sprintf("set%s", ucfirst($changedProperty));
-            $entity->$setter($changedValue);
-        }
-
-        return $entity;
-    }
-
     /**
      * The changed resource data, i.e the new values of the changed properties.
      */
diff --git a/src/DependencyInjection/Compiler/VersionedResourcePass.php b/src/DependencyInjection/Compiler/VersionedResourcePass.php
new file mode 100644
index 0000000..84272ed
--- /dev/null
+++ b/src/DependencyInjection/Compiler/VersionedResourcePass.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace App\DependencyInjection\Compiler;
+
+use App\Service\ApiResourceNormalizer;
+use App\Service\VersionedResourceService;
+use Gedmo\Mapping\Annotation as Gedmo;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+class VersionedResourcePass implements CompilerPassInterface
+{
+    public function process(ContainerBuilder $container): void
+    {
+        $allClasses = \get_declared_classes();
+        $entityClasses = \array_filter($allClasses, function (string $className) {
+            return \str_starts_with($className, 'App\\Entity\\');
+        });
+
+        $versionedResourceNames = [];
+        foreach ($entityClasses as $entityClass) {
+            $reflectionClass = new \ReflectionClass($entityClass);
+            $attributes = $reflectionClass->getAttributes(Gedmo\Loggable::class);
+
+            if (empty($attributes)) {
+                continue;
+            }
+
+            $versionedResourceNames = [
+                ...$versionedResourceNames,
+                ApiResourceNormalizer::toResource($entityClass)
+            ];
+        }
+
+        /** @var VersionedResourceService */
+        $versionedResourceService = $container->get(VersionedResourceService::class);
+        $versionedResourceService->compileNames($versionedResourceNames);
+    }
+}
diff --git a/src/Dto/GatewayCheckoutUpdateDto.php b/src/Dto/GatewayCheckoutUpdateDto.php
new file mode 100644
index 0000000..1ce5e7f
--- /dev/null
+++ b/src/Dto/GatewayCheckoutUpdateDto.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Dto;
+
+use App\Entity\GatewayCheckoutStatus;
+use Symfony\Component\Validator\Constraints as Assert;
+
+final class GatewayCheckoutUpdateDto
+{
+    /**
+     * The status of the checkout with the Gateway.
+     */
+    #[Assert\NotBlank()]
+    public GatewayCheckoutStatus $status;
+
+    /**
+     * An external identifier provided by the Gateway for the payment.
+     */
+    #[Assert\NotBlank()]
+    public string $gatewayReference;
+
+    public function __construct(
+        GatewayCheckoutStatus $status,
+        string $gatewayReference
+    ) {
+        $this->status = $status;
+        $this->gatewayReference = $gatewayReference;
+    }
+}
diff --git a/src/Entity/Accounting.php b/src/Entity/Accounting.php
index 54bae0a..89bc2b5 100644
--- a/src/Entity/Accounting.php
+++ b/src/Entity/Accounting.php
@@ -34,12 +34,8 @@ class Accounting
     private ?string $currency = null;
 
     #[API\ApiProperty(writable: false)]
-    #[ORM\OneToMany(mappedBy: 'origin', targetEntity: Transaction::class)]
-    private Collection $transactionsIssued;
-
-    #[API\ApiProperty(writable: false)]
-    #[ORM\OneToMany(mappedBy: 'target', targetEntity: Transaction::class)]
-    private Collection $transactionsReceived;
+    #[ORM\OneToMany(mappedBy: 'accounting', targetEntity: AccountingStatement::class)]
+    private Collection $statements;
 
     #[API\ApiProperty(writable: false, readable: false)]
     #[ORM\Column(length: 255)]
@@ -51,6 +47,9 @@ class Accounting
     #[ORM\OneToOne(mappedBy: 'accounting', cascade: ['persist', 'remove'])]
     private ?Project $project = null;
 
+    #[ORM\OneToOne(mappedBy: 'accounting', cascade: ['persist', 'remove'])]
+    private ?Tipjar $tipjar = null;
+
     public function __construct()
     {
         /**
@@ -58,9 +57,7 @@ class Accounting
          * ideally a configuration that can be updated via a frontend, not env var only
          */
         $this->currency = 'EUR';
-
-        $this->transactionsIssued = new ArrayCollection();
-        $this->transactionsReceived = new ArrayCollection();
+        $this->statements = new ArrayCollection();
     }
 
     public function getId(): ?int
@@ -81,59 +78,29 @@ class Accounting
     }
 
     /**
-     * @return Collection<int, Transaction>
+     * @return Collection<int, AccountingStatement>
      */
-    public function getTransactionsIssued(): Collection
+    public function getStatements(): Collection
     {
-        return $this->transactionsIssued;
+        return $this->statements;
     }
 
-    public function addTransactionsIssued(Transaction $transactionsIssued): static
+    public function addStatement(AccountingStatement $statement): static
     {
-        if (!$this->transactionsIssued->contains($transactionsIssued)) {
-            $this->transactionsIssued->add($transactionsIssued);
-            $transactionsIssued->setOrigin($this);
+        if (!$this->statements->contains($statement)) {
+            $this->statements->add($statement);
+            $statement->setAccounting($this);
         }
 
         return $this;
     }
 
-    public function removeTransactionsIssued(Transaction $transactionsIssued): static
+    public function removeStatement(AccountingStatement $statement): static
     {
-        if ($this->transactionsIssued->removeElement($transactionsIssued)) {
+        if ($this->statements->removeElement($statement)) {
             // set the owning side to null (unless already changed)
-            if ($transactionsIssued->getOrigin() === $this) {
-                $transactionsIssued->setOrigin(null);
-            }
-        }
-
-        return $this;
-    }
-
-    /**
-     * @return Collection<int, Transaction>
-     */
-    public function getTransactionsReceived(): Collection
-    {
-        return $this->transactionsReceived;
-    }
-
-    public function addTransactionsReceived(Transaction $transactionsReceived): static
-    {
-        if (!$this->transactionsReceived->contains($transactionsReceived)) {
-            $this->transactionsReceived->add($transactionsReceived);
-            $transactionsReceived->setTarget($this);
-        }
-
-        return $this;
-    }
-
-    public function removeTransactionsReceived(Transaction $transactionsReceived): static
-    {
-        if ($this->transactionsReceived->removeElement($transactionsReceived)) {
-            // set the owning side to null (unless already changed)
-            if ($transactionsReceived->getTarget() === $this) {
-                $transactionsReceived->setTarget(null);
+            if ($statement->getAccounting() === $this) {
+                $statement->setAccounting(null);
             }
         }
 
@@ -204,4 +171,24 @@ class Accounting
 
         return $this;
     }
+
+    public function getTipjar(): ?Tipjar
+    {
+        return $this->tipjar;
+    }
+
+    public function setTipjar(Tipjar $tipjar): static
+    {
+        // set the owning side of the relation if necessary
+        if ($tipjar->getAccounting() !== $this) {
+            $tipjar->setAccounting($this);
+        }
+
+        // set the owner class
+        $this->setOwnerClass($tipjar::class);
+
+        $this->tipjar = $tipjar;
+
+        return $this;
+    }
 }
diff --git a/src/Entity/AccountingStatement.php b/src/Entity/AccountingStatement.php
new file mode 100644
index 0000000..0d1daef
--- /dev/null
+++ b/src/Entity/AccountingStatement.php
@@ -0,0 +1,116 @@
+<?php
+
+namespace App\Entity;
+
+use ApiPlatform\Metadata as API;
+use App\Repository\AccountingStatementRepository;
+use Doctrine\ORM\Mapping as ORM;
+
+/**
+ * An AccountingStatement represents a change in the balance of an Accounting.\
+ * \
+ * When money is received, an Statement holds it as available.
+ * When money is issued, an Statement draws available money from previous statements.\
+ * \
+ * The sum of available money in the statements is the available money at that Accounting.
+ */
+#[API\GetCollection(
+    uriTemplate: '/accountings/{id}/statements',
+    uriVariables: [
+        'id' => new API\Link(fromClass: Accounting::class, toProperty: 'accounting'),
+    ],
+)]
+#[API\Get(
+    uriTemplate: '/accountings/{id}/statements/{statementId}',
+    uriVariables: [
+        'id' => new API\Link(fromClass: Accounting::class, toProperty: 'accounting'),
+        'statementId' => new API\Link(fromClass: AccountingStatement::class)
+    ],
+)]
+#[ORM\Entity(repositoryClass: AccountingStatementRepository::class)]
+class AccountingStatement
+{
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column]
+    private ?int $id = null;
+
+    #[API\ApiProperty(readable: false)]
+    #[ORM\ManyToOne(inversedBy: 'statements')]
+    #[ORM\JoinColumn(nullable: false)]
+    private ?Accounting $accounting = null;
+
+    /**
+     * The money held in this Statement.
+     */
+    #[ORM\Embedded(class: Money::class)]
+    private ?Money $money = null;
+
+    /**
+     * The direction of this Statement.\
+     * `incoming` means the transaction was received and the money is available.\
+     * `outgoing` means the transaction was issued and the money is an expenditure.
+     */
+    #[ORM\Column()]
+    private ?AccountingStatementDirection $direction = null;
+
+    /**
+     * The Transaction represented in this Statement.
+     */
+    #[ORM\OneToOne(cascade: ['persist', 'remove'])]
+    #[ORM\JoinColumn(nullable: false)]
+    private ?AccountingTransaction $transaction = null;
+
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
+    public function getAccounting(): ?Accounting
+    {
+        return $this->accounting;
+    }
+
+    public function setAccounting(?Accounting $accounting): static
+    {
+        $this->accounting = $accounting;
+
+        return $this;
+    }
+
+    public function getMoney(): ?Money
+    {
+        return $this->money;
+    }
+
+    public function setMoney(Money $money): static
+    {
+        $this->money = $money;
+
+        return $this;
+    }
+
+    public function getDirection(): ?AccountingStatementDirection
+    {
+        return $this->direction;
+    }
+
+    public function setDirection(AccountingStatementDirection $direction): static
+    {
+        $this->direction = $direction;
+
+        return $this;
+    }
+
+    public function getTransaction(): ?AccountingTransaction
+    {
+        return $this->transaction;
+    }
+
+    public function setTransaction(AccountingTransaction $transaction): static
+    {
+        $this->transaction = $transaction;
+
+        return $this;
+    }
+}
diff --git a/src/Entity/AccountingStatementDirection.php b/src/Entity/AccountingStatementDirection.php
new file mode 100644
index 0000000..d5a80cb
--- /dev/null
+++ b/src/Entity/AccountingStatementDirection.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace App\Entity;
+
+enum AccountingStatementDirection: string
+{
+    case Incoming = 'incoming';
+
+    case Outgoing = 'outgoing';
+}
diff --git a/src/Entity/Transaction.php b/src/Entity/AccountingTransaction.php
similarity index 64%
rename from src/Entity/Transaction.php
rename to src/Entity/AccountingTransaction.php
index 810b97a..1281365 100644
--- a/src/Entity/Transaction.php
+++ b/src/Entity/AccountingTransaction.php
@@ -2,8 +2,7 @@
 
 namespace App\Entity;
 
-use ApiPlatform\Metadata as API;
-use App\Repository\TransactionRepository;
+use App\Repository\AccountingTransactionRepository;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Component\Validator\Constraints as Assert;
 
@@ -13,10 +12,8 @@ use Symfony\Component\Validator\Constraints as Assert;
  * When a Transaction targets an Accounting it means that the Accounting receives it, this will add to that Accounting.
  * When a Transaction originates from an Accounting the Accounting issues the Transaction and it will deduct from it.
  */
-#[ORM\Entity(repositoryClass: TransactionRepository::class)]
-#[API\GetCollection()]
-#[API\Get()]
-class Transaction
+#[ORM\Entity(repositoryClass: AccountingTransactionRepository::class)]
+class AccountingTransaction
 {
     #[ORM\Id]
     #[ORM\GeneratedValue]
@@ -47,20 +44,6 @@ class Transaction
     #[ORM\JoinColumn(nullable: false)]
     private ?Accounting $target = null;
 
-    /**
-     * The name of the Gateway implementation that secured the money in this Transaction.
-     */
-    #[Assert\NotBlank()]
-    #[ORM\Column(length: 255)]
-    private ?string $gateway = null;
-
-    /**
-     * An external identifier provided by the Gateway for this Transaction.
-     */
-    #[Assert\NotBlank()]
-    #[ORM\Column(length: 255)]
-    private ?string $gatewayReference = null;
-
     public function getId(): ?int
     {
         return $this->id;
@@ -101,28 +84,4 @@ class Transaction
 
         return $this;
     }
-
-    public function getGateway(): ?string
-    {
-        return $this->gateway;
-    }
-
-    public function setGateway(string $gateway): static
-    {
-        $this->gateway = $gateway;
-
-        return $this;
-    }
-
-    public function getGatewayReference(): ?string
-    {
-        return $this->gatewayReference;
-    }
-
-    public function setGatewayReference(string $gatewayReference): static
-    {
-        $this->gatewayReference = $gatewayReference;
-
-        return $this;
-    }
 }
diff --git a/src/Entity/GatewayCharge.php b/src/Entity/GatewayCharge.php
index 7ae246a..6bed9ab 100644
--- a/src/Entity/GatewayCharge.php
+++ b/src/Entity/GatewayCharge.php
@@ -2,11 +2,13 @@
 
 namespace App\Entity;
 
-use ApiPlatform\Metadata as API;
 use App\Repository\GatewayChargeRepository;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Component\Validator\Constraints as Assert;
 
+/**
+ * A GatewayCharge represents a monetary payment that can be done by an issuer at checkout with the Gateway.
+ */
 #[ORM\Entity(repositoryClass: GatewayChargeRepository::class)]
 class GatewayCharge
 {
@@ -16,37 +18,44 @@ class GatewayCharge
     private ?int $id = null;
 
     /**
-     * The money to be charged by the Gateway at checkout.
+     * The type of a GatewayCharge represents the kind of payment.
      */
     #[Assert\NotBlank()]
-    #[ORM\Embedded(class: Money::class)]
+    #[ORM\Column()]
+    private ?GatewayChargeType $type = null;
+
+    /**
+     * The charged monetary sum.
+     */
+    #[Assert\NotBlank()]
+    #[ORM\Embedded(Money::class)]
     private ?Money $money = null;
 
     /**
-     * The Accounting that will receive the Transaction of this GatewayCharge after a successful checkout.
+     * The Accounting receiving the consequent Transaction for this GatewayCharge.
      */
     #[Assert\NotBlank()]
     #[ORM\ManyToOne]
     #[ORM\JoinColumn(nullable: false)]
     private ?Accounting $target = null;
 
-    /**
-     * Custom data to be passed to the Gateway.\
-     * E.g: billing period, product name, custom metadata, etc.
-     */
-    #[ORM\Column(nullable: true)]
-    private ?array $extradata = null;
-
-    #[API\ApiProperty(writable: false)]
-    #[ORM\ManyToOne(inversedBy: 'charges')]
-    #[ORM\JoinColumn(nullable: false)]
-    private ?GatewayCheckout $checkout = null;
-
     public function getId(): ?int
     {
         return $this->id;
     }
 
+    public function getType(): ?GatewayChargeType
+    {
+        return $this->type;
+    }
+
+    public function setType(GatewayChargeType $type): static
+    {
+        $this->type = $type;
+
+        return $this;
+    }
+
     public function getMoney(): ?Money
     {
         return $this->money;
@@ -70,28 +79,4 @@ class GatewayCharge
 
         return $this;
     }
-
-    public function getExtradata(): ?array
-    {
-        return $this->extradata;
-    }
-
-    public function setExtradata(?array $extradata): static
-    {
-        $this->extradata = $extradata;
-
-        return $this;
-    }
-
-    public function getCheckout(): ?GatewayCheckout
-    {
-        return $this->checkout;
-    }
-
-    public function setCheckout(?GatewayCheckout $checkout): static
-    {
-        $this->checkout = $checkout;
-
-        return $this;
-    }
 }
diff --git a/src/Entity/GatewayChargeType.php b/src/Entity/GatewayChargeType.php
new file mode 100644
index 0000000..84c7ba1
--- /dev/null
+++ b/src/Entity/GatewayChargeType.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace App\Entity;
+
+enum GatewayChargeType: string
+{
+    /**
+     * A one-time charge to the money payer.
+     */
+    case Single = 'single';
+
+    /**
+     * A recurring charge to the money payer.
+     */
+    case Recurring = 'recurring';
+}
diff --git a/src/Entity/GatewayCheckout.php b/src/Entity/GatewayCheckout.php
index 4b7a073..0611269 100644
--- a/src/Entity/GatewayCheckout.php
+++ b/src/Entity/GatewayCheckout.php
@@ -2,62 +2,117 @@
 
 namespace App\Entity;
 
+use ApiPlatform\Doctrine\Orm\Filter\SearchFilter;
 use ApiPlatform\Metadata as API;
+use App\Dto\GatewayCheckoutUpdateDto;
 use App\Repository\GatewayCheckoutRepository;
 use App\State\GatewayCheckoutProcessor;
+use App\State\GatewayCheckoutUpdateProcessor;
 use App\Validator\GatewayName;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
+use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping as ORM;
+use Gedmo\Mapping\Annotation as Gedmo;
+use Gedmo\Timestampable\Traits\TimestampableEntity;
 use Symfony\Component\Validator\Constraints as Assert;
 
 /**
  * A GatewayCheckout bundles the data to perform a charge operation at a Gateway.
  * Use it in order to create Transactions and have the transferred money be backed by a Gateway's payment processing.
  */
+#[Gedmo\Loggable()]
 #[API\GetCollection()]
-#[API\Post(processor: GatewayCheckoutProcessor::class)]
+#[API\Post(processor: GatewayCheckoutProcessor::class, validationContext: ['groups' => ['default', 'postValidation']])]
 #[API\Get()]
+#[API\Patch(input: GatewayCheckoutUpdateDto::class, processor: GatewayCheckoutUpdateProcessor::class)]
+#[API\ApiFilter(filterClass: SearchFilter::class, properties: ['origin' => 'exact', 'charges.target' => 'exact'])]
 #[ORM\Entity(repositoryClass: GatewayCheckoutRepository::class)]
 class GatewayCheckout
 {
+    use TimestampableEntity;
+
     #[ORM\Id]
     #[ORM\GeneratedValue]
     #[ORM\Column]
     private ?int $id = null;
 
-    /**
-     * The name of the Gateway implementation to checkout with.
-     */
-    #[GatewayName]
-    #[Assert\NotBlank()]
-    #[ORM\Column(length: 255)]
-    private ?string $gateway = null;
-
     /**
      * The Accounting that will issue the Transactions of the GatewayCharges after a successful checkout.
      */
     #[Assert\NotBlank()]
+    #[API\ApiProperty(readableLink: true)]
     #[ORM\ManyToOne]
     #[ORM\JoinColumn(nullable: false)]
     private ?Accounting $origin = null;
 
     /**
-     * The charges to be made by the Gateway at checkout.\
-     * Each GatewayCharge will generate a separate Transaction after a successful checkout.
+     * The GatewayCharges to be charged at checkout with the Gateway.
      */
     #[Assert\NotBlank()]
     #[Assert\Count(min: 1)]
-    #[ORM\OneToMany(
-        mappedBy: 'checkout',
-        targetEntity: GatewayCharge::class,
-        cascade: ['persist']
-    )]
+    #[API\ApiProperty(readableLink: true, writableLink: true)]
+    #[ORM\ManyToMany(targetEntity: GatewayCharge::class, cascade: ['persist'])]
     private Collection $charges;
 
+    /**
+     * The status of the checkout with the Gateway.
+     */
+    #[Gedmo\Versioned]
+    #[API\ApiProperty(writable: false)]
+    #[API\ApiFilter(SearchFilter::class)]
+    #[ORM\Column()]
+    private ?GatewayCheckoutStatus $status = null;
+
+    /**
+     * The name of the Gateway implementation to checkout with.
+     */
+    #[GatewayName]
+    #[Assert\NotBlank()]
+    #[API\ApiFilter(SearchFilter::class)]
+    #[ORM\Column(length: 255)]
+    private ?string $gateway = null;
+
+    /**
+     * An external identifier provided by the Gateway for the payment.\
+     * Required when a GatewayCheckout is completed.
+     */
+    #[Assert\NotBlank(['groups' => ['postValidation']])]
+    #[API\ApiFilter(SearchFilter::class)]
+    #[ORM\Column(length: 255)]
+    private ?string $gatewayReference = null;
+
+    /**
+     * The URL where the checkout with the Gateway is available.
+     */
+    #[API\ApiProperty(writable: false)]
+    #[ORM\Column(type: Types::TEXT)]
+    private ?string $checkoutUrl = null;
+
+    /**
+     * GatewayCheckout was migrated from an invest record in Goteo v3 platform. 
+     */
+    #[API\ApiProperty(writable: false)]
+    #[ORM\Column]
+    private ?bool $migrated = null;
+
+    /**
+     * The id of the original invest record in the Goteo v3 platform.
+     */
+    #[API\ApiProperty(writable: false)]
+    #[ORM\Column(length: 255, nullable: true)]
+    private ?string $migratedReference = null;
+
+    /**
+     * A free-form collection of additional data associated with this checkout operation.
+     */
+    #[ORM\Column(nullable: true)]
+    private ?array $metadata = null;
+
     public function __construct()
     {
         $this->charges = new ArrayCollection();
+        $this->status = GatewayCheckoutStatus::Pending;
     }
 
     public function getId(): ?int
@@ -65,18 +120,6 @@ class GatewayCheckout
         return $this->id;
     }
 
-    public function getGateway(): ?string
-    {
-        return $this->gateway;
-    }
-
-    public function setGateway(string $gateway): static
-    {
-        $this->gateway = $gateway;
-
-        return $this;
-    }
-
     public function getOrigin(): ?Accounting
     {
         return $this->origin;
@@ -101,7 +144,6 @@ class GatewayCheckout
     {
         if (!$this->charges->contains($charge)) {
             $this->charges->add($charge);
-            $charge->setCheckout($this);
         }
 
         return $this;
@@ -109,12 +151,91 @@ class GatewayCheckout
 
     public function removeCharge(GatewayCharge $charge): static
     {
-        if ($this->charges->removeElement($charge)) {
-            // set the owning side to null (unless already changed)
-            if ($charge->getCheckout() === $this) {
-                $charge->setCheckout(null);
-            }
-        }
+        $this->charges->removeElement($charge);
+
+        return $this;
+    }
+
+    public function getStatus(): ?GatewayCheckoutStatus
+    {
+        return $this->status;
+    }
+
+    public function setStatus(GatewayCheckoutStatus $status): static
+    {
+        $this->status = $status;
+
+        return $this;
+    }
+
+    public function getGateway(): ?string
+    {
+        return $this->gateway;
+    }
+
+    public function setGateway(string $gateway): static
+    {
+        $this->gateway = $gateway;
+
+        return $this;
+    }
+
+    public function getGatewayReference(): ?string
+    {
+        return $this->gatewayReference;
+    }
+
+    public function setGatewayReference(string $gatewayReference): static
+    {
+        $this->gatewayReference = $gatewayReference;
+
+        return $this;
+    }
+
+    public function getCheckoutUrl(): ?string
+    {
+        return $this->checkoutUrl;
+    }
+
+    public function setCheckoutUrl(string $checkoutUrl): static
+    {
+        $this->checkoutUrl = $checkoutUrl;
+
+        return $this;
+    }
+
+    public function isMigrated(): ?bool
+    {
+        return $this->migrated;
+    }
+
+    public function setMigrated(bool $migrated): static
+    {
+        $this->migrated = $migrated;
+
+        return $this;
+    }
+
+    public function getMigratedReference(): ?string
+    {
+        return $this->migratedReference;
+    }
+
+    public function setMigratedReference(?string $migratedReference): static
+    {
+        $this->migratedReference = $migratedReference;
+
+        return $this;
+    }
+
+    public function getMetadata(): ?array
+    {
+        return $this->metadata;
+    }
+
+    public function setMetadata(?array $metadata): static
+    {
+        $this->metadata = $metadata;
 
         return $this;
     }
diff --git a/src/Entity/GatewayCheckoutStatus.php b/src/Entity/GatewayCheckoutStatus.php
new file mode 100644
index 0000000..4e8bc86
--- /dev/null
+++ b/src/Entity/GatewayCheckoutStatus.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace App\Entity;
+
+enum GatewayCheckoutStatus: string
+{
+    case Pending = 'pending';
+
+    case Charged = 'charged';
+}
diff --git a/src/Entity/Project.php b/src/Entity/Project.php
index 1b89953..7e8d765 100644
--- a/src/Entity/Project.php
+++ b/src/Entity/Project.php
@@ -104,7 +104,7 @@ class Project
         return $this->owner;
     }
 
-    public function setOwner(User $owner): static
+    public function setOwner(?User $owner): static
     {
         $this->owner = $owner;
 
diff --git a/src/Entity/Tipjar.php b/src/Entity/Tipjar.php
new file mode 100644
index 0000000..57507f9
--- /dev/null
+++ b/src/Entity/Tipjar.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace App\Entity;
+
+use ApiPlatform\Metadata as API;
+use App\Repository\TipjarRepository;
+use Doctrine\ORM\Mapping as ORM;
+use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
+
+/**
+ * Unlike other Money recipients a Tipjar receives money with no further goal.\
+ * \
+ * Tips to the platform owners and other no-purpose money can target a Tipjar.
+ */
+#[UniqueEntity(fields: ['name'], message: 'A Tipjar with that name already exists.')]
+#[API\ApiResource]
+#[ORM\Entity(repositoryClass: TipjarRepository::class)]
+class Tipjar
+{
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column]
+    private ?int $id = null;
+
+    /**
+     * Human readable, non white space, unique string.
+     */
+    #[ORM\Column(length: 255)]
+    private ?string $name = null;
+
+    #[ORM\OneToOne(inversedBy: 'tipjar', cascade: ['persist', 'remove'])]
+    #[ORM\JoinColumn(nullable: false)]
+    private ?Accounting $accounting = null;
+
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
+    public function getName(): ?string
+    {
+        return $this->name;
+    }
+
+    public function setName(string $name): static
+    {
+        $this->name = $name;
+
+        return $this;
+    }
+
+    public function getAccounting(): ?Accounting
+    {
+        return $this->accounting;
+    }
+
+    public function setAccounting(Accounting $accounting): static
+    {
+        $this->accounting = $accounting;
+
+        return $this;
+    }
+}
diff --git a/src/Entity/TransactionGateway.php b/src/Entity/TransactionGateway.php
deleted file mode 100644
index 92962f3..0000000
--- a/src/Entity/TransactionGateway.php
+++ /dev/null
@@ -1,68 +0,0 @@
-<?php
-
-namespace App\Entity;
-
-use ApiPlatform\Metadata as API;
-use App\Validator\GatewayName;
-use Doctrine\ORM\Mapping as ORM;
-use Symfony\Component\Validator\Constraints as Assert;
-
-/**
- * GatewayCheckouts represent an User's attempt to perform a payment with an specific Gateway.
- */
-#[ORM\Embeddable]
-class TransactionGateway
-{
-    /**
-     * The Gateway processing this Transaction.
-     */
-    #[GatewayName]
-    #[Assert\NotBlank()]
-    #[ORM\Column(length: 255)]
-    private ?string $name = null;
-
-    #[Assert\NotBlank()]
-    #[Assert\Url()]
-    #[ORM\Column(length: 255)]
-    private ?string $successUrl;
-
-    #[Assert\Url()]
-    #[ORM\Column(length: 255)]
-    private ?string $failureUrl;
-
-    public function getName(): ?string
-    {
-        return $this->name;
-    }
-
-    public function setName(string $name): static
-    {
-        $this->name = $name;
-
-        return $this;
-    }
-
-    public function getSuccessUrl(): ?string
-    {
-        return $this->successUrl;
-    }
-
-    public function setSuccessUrl(string $successUrl): static
-    {
-        $this->successUrl = $successUrl;
-
-        return $this;
-    }
-
-    public function getFailureUrl(): ?string
-    {
-        return $this->failureUrl;
-    }
-
-    public function setFailureUrl(string $failureUrl): static
-    {
-        $this->failureUrl = $failureUrl;
-
-        return $this;
-    }
-}
diff --git a/src/Filter/VersionResourceFilter.php b/src/Filter/ResourceVersionResourceFilter.php
similarity index 83%
rename from src/Filter/VersionResourceFilter.php
rename to src/Filter/ResourceVersionResourceFilter.php
index fe7b33d..1c33eba 100644
--- a/src/Filter/VersionResourceFilter.php
+++ b/src/Filter/ResourceVersionResourceFilter.php
@@ -5,19 +5,21 @@ namespace App\Filter;
 use ApiPlatform\Doctrine\Orm\Filter\AbstractFilter;
 use ApiPlatform\Doctrine\Orm\Util\QueryNameGeneratorInterface;
 use ApiPlatform\Metadata\Operation;
+use App\Service\VersionedResourceService;
 use Doctrine\ORM\QueryBuilder;
 use Doctrine\Persistence\ManagerRegistry;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\PropertyInfo\Type;
 use Symfony\Component\Serializer\NameConverter\NameConverterInterface;
 
-final class VersionResourceFilter extends AbstractFilter
+final class ResourceVersionResourceFilter extends AbstractFilter
 {
     public function __construct(
+        private VersionedResourceService $versionedResourceService,
         protected ManagerRegistry $managerRegistry,
         ?LoggerInterface $logger = null,
         protected ?array $properties = null,
-        protected ?NameConverterInterface $nameConverter = null
+        protected ?NameConverterInterface $nameConverter = null,
     ) {
         parent::__construct($managerRegistry, $logger, $properties, $nameConverter);
     }
@@ -45,7 +47,7 @@ final class VersionResourceFilter extends AbstractFilter
                 'description' => 'The name of the resource.',
                 'schema' => [
                     'type' => Type::BUILTIN_TYPE_STRING,
-                    'enum' => ['User']
+                    'enum' => $this->versionedResourceService->getNames()
                 ],
                 'openapi' => [
                     'allowEmptyValue' => false,
diff --git a/src/Filter/VersionResourceIdFilter.php b/src/Filter/ResourceVersionResourceIdFilter.php
similarity index 94%
rename from src/Filter/VersionResourceIdFilter.php
rename to src/Filter/ResourceVersionResourceIdFilter.php
index 0b68986..3f699a9 100644
--- a/src/Filter/VersionResourceIdFilter.php
+++ b/src/Filter/ResourceVersionResourceIdFilter.php
@@ -8,7 +8,7 @@ use ApiPlatform\Metadata\Operation;
 use Doctrine\ORM\QueryBuilder;
 use Symfony\Component\PropertyInfo\Type;
 
-final class VersionResourceIdFilter extends AbstractFilter
+final class ResourceVersionResourceIdFilter extends AbstractFilter
 {
     protected function filterProperty(
         string $property,
diff --git a/src/Kernel.php b/src/Kernel.php
index d8bf758..0388b2a 100644
--- a/src/Kernel.php
+++ b/src/Kernel.php
@@ -3,6 +3,7 @@
 namespace App;
 
 use App\DependencyInjection\Compiler\GatewayPass;
+use App\DependencyInjection\Compiler\VersionedResourcePass;
 use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
 use Symfony\Component\DependencyInjection\Compiler\PassConfig;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
@@ -18,5 +19,10 @@ class Kernel extends BaseKernel
             new GatewayPass,
             PassConfig::TYPE_AFTER_REMOVING
         );
+
+        $container->addCompilerPass(
+            new VersionedResourcePass,
+            PassConfig::TYPE_AFTER_REMOVING
+        );
     }
 }
diff --git a/src/Library/Benzina/Pump/CheckoutsPump.php b/src/Library/Benzina/Pump/CheckoutsPump.php
new file mode 100644
index 0000000..e113865
--- /dev/null
+++ b/src/Library/Benzina/Pump/CheckoutsPump.php
@@ -0,0 +1,268 @@
+<?php
+
+namespace App\Library\Benzina\Pump;
+
+use App\Entity\Accounting;
+use App\Entity\GatewayCharge;
+use App\Entity\GatewayChargeType;
+use App\Entity\GatewayCheckout;
+use App\Entity\GatewayCheckoutStatus;
+use App\Entity\Money;
+use App\Entity\Tipjar;
+use App\Library\Benzina\Pump\Trait\ArrayPumpTrait;
+use App\Library\Benzina\Pump\Trait\ProgressivePumpTrait;
+use App\Library\Economy\Payment\CashGateway;
+use App\Library\Economy\Payment\CecaGateway;
+use App\Library\Economy\Payment\DropGateway;
+use App\Library\Economy\Payment\PaypalGateway;
+use App\Library\Economy\Payment\StripeGateway;
+use App\Library\Economy\Payment\WalletGateway;
+use App\Repository\ProjectRepository;
+use App\Repository\TipjarRepository;
+use App\Repository\UserRepository;
+use Doctrine\ORM\EntityManagerInterface;
+
+class CheckoutsPump implements PumpInterface
+{
+    use ArrayPumpTrait;
+    use ProgressivePumpTrait;
+
+    private const PLATFORM_TIPJAR_NAME = 'platform';
+    private const CHECKOUT_URL_DEFAULT = 'https://www.goteo.org/invest';
+
+    private const MAX_INT = 2147483647;
+
+    private const INVEST_KEYS = [
+        'id',
+        'user',
+        'project',
+        'account',
+        'amount',
+        'amount_original',
+        'currency',
+        'currency_rate',
+        'donate_amount',
+        'status',
+        'anonymous',
+        'resign',
+        'invested',
+        'charged',
+        'returned',
+        'preapproval',
+        'payment',
+        'transaction',
+        'method',
+        'admin',
+        'campaign',
+        'datetime',
+        'drops',
+        'droped',
+        'call',
+        'matcher',
+        'issue',
+        'pool',
+        'extra_info'
+    ];
+
+    public function __construct(
+        private UserRepository $userRepository,
+        private ProjectRepository $projectRepository,
+        private TipjarRepository $tipjarRepository,
+        private EntityManagerInterface $entityManager
+    ) {
+    }
+
+    public function supports(mixed $data): bool
+    {
+        if (!\is_array($data) || !\array_key_exists(0, $data)) {
+            return false;
+        }
+
+        return $this->hasAllKeys($data[0], self::INVEST_KEYS);
+    }
+
+    public function process(mixed $data): void
+    {
+        $users = $this->getUsers($data);
+        $projects = $this->getProjects($data);
+
+        $tipjar = $this->getPlatformTipjar();
+
+        $pumped = $this->getPumped(GatewayCheckout::class, $data, ['migratedReference' => 'id']);
+
+        foreach ($data as $key => $record) {
+            if ($this->isPumped($record, $pumped)) {
+                continue;
+            }
+
+            if (!\array_key_exists($record['project'], $projects)) {
+                continue;
+            }
+
+            if (!$record['amount'] || $record['amount'] < 1) {
+                continue;
+            }
+
+            if (!$record['method'] || empty($record['method'])) {
+                continue;
+            }
+
+            $user = $users[$record['user']];
+            $project = $projects[$record['project']];
+
+            $checkout = new GatewayCheckout;
+            $checkout->setOrigin($user->getAccounting());
+            $checkout->setStatus($this->getCheckoutStatus($record));
+            $checkout->setGateway($this->getCheckoutGateway($record));
+            $checkout->setGatewayReference($this->getCheckoutReference($record));
+            $checkout->setCheckoutUrl(self::CHECKOUT_URL_DEFAULT);
+            $checkout->setMigrated(true);
+            $checkout->setMigratedReference($record['id']);
+            $checkout->setMetadata([
+                'payment' => $record['payment'],
+                'transaction' => $record['transaction'],
+                'preapproval' => $record['preapproval']
+            ]);
+            $checkout->setCreatedAt(new \DateTime($record['invested']));
+            $checkout->setUpdatedAt(new \DateTime());
+
+            $charge = new GatewayCharge;
+            $charge->setType($this->getChargeType($record));
+            $charge->setMoney($this->getChargeMoney($record['amount'], $record['currency']));
+            $charge->setTarget($project->getAccounting());
+
+            if ($record['donate_amount'] > 0) {
+                $tip = new GatewayCharge;
+                $tip->setType(GatewayChargeType::Single);
+                $tip->setMoney($this->getChargeMoney($record['donate_amount'], $record['currency']));
+                $tip->setTarget($tipjar->getAccounting());
+
+                $this->entityManager->persist($tip);
+                $checkout->addCharge($tip);
+            }
+
+            $this->entityManager->persist($charge);
+            $checkout->addCharge($charge);
+
+            $this->entityManager->persist($checkout);
+        }
+
+        $this->entityManager->flush();
+        $this->entityManager->clear();
+    }
+
+    private function getUsers(array $data): array
+    {
+        $users = $this->userRepository->findBy(['migratedReference' => \array_map(function ($data) {
+            return $data['user'];
+        }, $data)]);
+
+        $usersByMigratedReference = [];
+        foreach ($users as $user) {
+            $usersByMigratedReference[$user->getMigratedReference()] = $user;
+        }
+
+        return $usersByMigratedReference;
+    }
+
+    private function getProjects(array $data): array
+    {
+        $projects = $this->projectRepository->findBy(['migratedReference' => \array_map(function ($data) {
+            return $data['project'];
+        }, $data)]);
+
+        $projectsByMigratedReference = [];
+        foreach ($projects as $project) {
+            $projectsByMigratedReference[$project->getMigratedReference()] = $project;
+        }
+
+        return $projectsByMigratedReference;
+    }
+
+    private function getPlatformTipjar(): Tipjar
+    {
+        $tipjar = $this->tipjarRepository->findOneBy(['name' => self::PLATFORM_TIPJAR_NAME]);
+
+        if ($tipjar) {
+            return $tipjar;
+        }
+
+        $tipjar = new Tipjar;
+        $tipjar->setName(SELF::PLATFORM_TIPJAR_NAME);
+
+        $accounting = new Accounting;
+        $accounting->setTipjar($tipjar);
+
+        $this->entityManager->persist($tipjar);
+        $this->entityManager->persist($accounting);
+        $this->entityManager->flush();
+
+        return $tipjar;
+    }
+
+    private function getChargeType(array $record): GatewayChargeType
+    {
+        if (\in_array($record['method'], ['stripe_subscription'])) {
+            return GatewayChargeType::Recurring;
+        }
+
+        return GatewayChargeType::Single;
+    }
+
+    private function getChargeMoney(int $amount, string $currency): Money
+    {
+        $amount = $amount * 100;
+
+        if ($amount >= self::MAX_INT) {
+            $amount = self::MAX_INT;
+        }
+
+        return new Money($amount, $currency);
+    }
+
+    private function getCheckoutStatus(array $record): GatewayCheckoutStatus
+    {
+        if ($record['status'] < 1) {
+            return GatewayCheckoutStatus::Pending;
+        }
+
+        return GatewayCheckoutStatus::Charged;
+    }
+
+    private function getCheckoutGateway(array $record): string
+    {
+        switch ($record['method']) {
+            case 'stripe_subscription':
+                return StripeGateway::getName();
+            case 'pool':
+                return WalletGateway::getName();
+            case 'paypal':
+                return PaypalGateway::getName();
+            case 'tpv':
+                return CecaGateway::getName();
+            case 'cash':
+                return CashGateway::getName();
+            case 'drop':
+                return DropGateway::getName();
+            default:
+                return '';
+        }
+    }
+
+    private function getCheckoutReference(array $record): string
+    {
+        if (!empty($record['payment'])) {
+            return $record['payment'];
+        }
+
+        if (!empty($record['transaction'])) {
+            return $record['transaction'];
+        }
+
+        if (!empty($record['preapproval'])) {
+            return $record['preapproval'];
+        }
+
+        return '';
+    }
+}
diff --git a/src/Library/Benzina/Pump/ProjectsPump.php b/src/Library/Benzina/Pump/ProjectsPump.php
index f0c54b0..1a6e4cf 100644
--- a/src/Library/Benzina/Pump/ProjectsPump.php
+++ b/src/Library/Benzina/Pump/ProjectsPump.php
@@ -6,6 +6,8 @@ use App\Entity\Accounting;
 use App\Entity\Project;
 use App\Entity\ProjectStatus;
 use App\Entity\User;
+use App\Library\Benzina\Pump\Trait\ArrayPumpTrait;
+use App\Library\Benzina\Pump\Trait\ProgressivePumpTrait;
 use App\Repository\UserRepository;
 use Doctrine\ORM\EntityManagerInterface;
 
@@ -131,6 +133,8 @@ class ProjectsPump implements PumpInterface
             $project->setStatus($this->getProjectStatus($record['status']));
             $project->setMigrated(true);
             $project->setMigratedReference($record['id']);
+            $project->setCreatedAt(new \DateTime($record['created']));
+            $project->setUpdatedAt(new \DateTime());
 
             $accounting = $this->getAccounting($record);
             $accounting->setProject($project);
diff --git a/src/Library/Benzina/Pump/ArrayPumpTrait.php b/src/Library/Benzina/Pump/Trait/ArrayPumpTrait.php
similarity index 91%
rename from src/Library/Benzina/Pump/ArrayPumpTrait.php
rename to src/Library/Benzina/Pump/Trait/ArrayPumpTrait.php
index 1903820..64d5c8b 100644
--- a/src/Library/Benzina/Pump/ArrayPumpTrait.php
+++ b/src/Library/Benzina/Pump/Trait/ArrayPumpTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace App\Library\Benzina\Pump;
+namespace App\Library\Benzina\Pump\Trait;
 
 trait ArrayPumpTrait
 {
diff --git a/src/Library/Benzina/Pump/ProgressivePumpTrait.php b/src/Library/Benzina/Pump/Trait/ProgressivePumpTrait.php
similarity index 97%
rename from src/Library/Benzina/Pump/ProgressivePumpTrait.php
rename to src/Library/Benzina/Pump/Trait/ProgressivePumpTrait.php
index fb1d87d..3452b51 100644
--- a/src/Library/Benzina/Pump/ProgressivePumpTrait.php
+++ b/src/Library/Benzina/Pump/Trait/ProgressivePumpTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace App\Library\Benzina\Pump;
+namespace App\Library\Benzina\Pump\Trait;
 
 use Doctrine\ORM\EntityManagerInterface;
 
diff --git a/src/Library/Benzina/Pump/UsersPump.php b/src/Library/Benzina/Pump/UsersPump.php
index f8011b1..92802cd 100644
--- a/src/Library/Benzina/Pump/UsersPump.php
+++ b/src/Library/Benzina/Pump/UsersPump.php
@@ -4,6 +4,8 @@ namespace App\Library\Benzina\Pump;
 
 use App\Entity\Accounting;
 use App\Entity\User;
+use App\Library\Benzina\Pump\Trait\ArrayPumpTrait;
+use App\Library\Benzina\Pump\Trait\ProgressivePumpTrait;
 use Doctrine\ORM\EntityManagerInterface;
 
 class UsersPump implements PumpInterface
@@ -72,6 +74,7 @@ class UsersPump implements PumpInterface
             }
 
             $user = new User;
+            $user->setAccounting(new Accounting);
             $user->setUsername($this->getUsername($record));
             $user->setPassword($record['password'] ?? "");
             $user->setEmail($record['email']);
diff --git a/src/Library/Economy/Currency/EuropeanCentralBankExchange.php b/src/Library/Economy/Currency/EuropeanCentralBankExchange.php
index f51e298..9d2e2fc 100644
--- a/src/Library/Economy/Currency/EuropeanCentralBankExchange.php
+++ b/src/Library/Economy/Currency/EuropeanCentralBankExchange.php
@@ -25,7 +25,7 @@ class EuropeanCentralBankExchange implements ExchangeInterface
 
     public function __construct()
     {
-        $data = json_decode(json_encode(\simplexml_load_file(self::ECB_DATA)), true)['Cube']['Cube'];
+        $data = $this->getData();
 
         $this->date = \DateTime::createFromFormat(
             \DateTimeInterface::RFC3339,
@@ -33,7 +33,6 @@ class EuropeanCentralBankExchange implements ExchangeInterface
             new \DateTimeZone('CET')
         );
 
-
         $provider = new ConfigurableProvider();
         foreach ($data['Cube'] as $item) {
             $rate = $item['@attributes'];
@@ -44,6 +43,38 @@ class EuropeanCentralBankExchange implements ExchangeInterface
         $this->converter = new CurrencyConverter($this->provider);
     }
 
+    private function getDataLatest(): array
+    {
+        $data = \simplexml_load_file(self::ECB_DATA);
+        if (!$data) {
+            throw new \Exception("Could not retrieve XML data");
+        }
+
+        return \json_decode(\json_encode($data), true)['Cube']['Cube'];
+    }
+
+    private function getDataCached(): array
+    {
+        $data = \apcu_fetch(self::ECB_DATA);
+        if (!$data) {
+            throw new \Exception("Could not retrieve cached data");
+        }
+
+        return \json_decode($data, true);
+    }
+
+    public function getData(): array
+    {
+        try {
+            return $this->getDataCached();
+        } catch (\Exception $e) {
+            $data = $this->getDataLatest();
+
+            \apcu_store(self::ECB_DATA, json_encode($data));
+            return $this->getData();
+        }
+    }
+
     public function getName(): string
     {
         return 'european_central_bank';
@@ -71,7 +102,7 @@ class EuropeanCentralBankExchange implements ExchangeInterface
 
     public function getConversionRate(string $source, string $target): float
     {
-        return $this->provider->getExchangeRate($source, $target);
+        return $this->provider->getExchangeRate($source, $target)->toFloat();
     }
 
     public function getConversionDate(string $source, string $target): \DateTimeInterface
diff --git a/src/Library/Economy/Payment/CashGateway.php b/src/Library/Economy/Payment/CashGateway.php
new file mode 100644
index 0000000..9b24ecb
--- /dev/null
+++ b/src/Library/Economy/Payment/CashGateway.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Library\Economy\Payment;
+
+abstract class CashGateway implements GatewayInterface
+{
+    public static function getName(): string
+    {
+        return 'cash';
+    }
+}
diff --git a/src/Library/Economy/Payment/CecaGateway.php b/src/Library/Economy/Payment/CecaGateway.php
new file mode 100644
index 0000000..81ce1ff
--- /dev/null
+++ b/src/Library/Economy/Payment/CecaGateway.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Library\Economy\Payment;
+
+abstract class CecaGateway implements GatewayInterface
+{
+    public static function getName(): string
+    {
+        return 'tpv';
+    }
+}
diff --git a/src/Library/Economy/Payment/DropGateway.php b/src/Library/Economy/Payment/DropGateway.php
new file mode 100644
index 0000000..135d367
--- /dev/null
+++ b/src/Library/Economy/Payment/DropGateway.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Library\Economy\Payment;
+
+abstract class DropGateway implements GatewayInterface
+{
+    public static function getName(): string
+    {
+        return 'drop';
+    }
+}
diff --git a/src/Library/Economy/Payment/GatewayInterface.php b/src/Library/Economy/Payment/GatewayInterface.php
index 8e26a34..d579da1 100644
--- a/src/Library/Economy/Payment/GatewayInterface.php
+++ b/src/Library/Economy/Payment/GatewayInterface.php
@@ -12,11 +12,11 @@ interface GatewayInterface
     public static function getName(): string;
 
     /**
-     * When processing a GatewayCheckout a Gateway must validate it using it's own means.
+     * Connects with the payment gateway and creates a checkout session to process payment.
      * 
      * Gateways are trusted to have secured the funds in the GatewayCheckout.
      * @param GatewayCheckout $checkout
      * @return GatewayCheckout
      */
-    public function process(GatewayCheckout $checkout): GatewayCheckout;
+    public function create(GatewayCheckout $checkout): GatewayCheckout;
 }
diff --git a/src/Library/Economy/Payment/PaypalGateway.php b/src/Library/Economy/Payment/PaypalGateway.php
new file mode 100644
index 0000000..934ecad
--- /dev/null
+++ b/src/Library/Economy/Payment/PaypalGateway.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Library\Economy\Payment;
+
+abstract class PaypalGateway implements GatewayInterface
+{
+    public static function getName(): string
+    {
+        return 'paypal';
+    }
+}
diff --git a/src/Repository/AccountingStatementRepository.php b/src/Repository/AccountingStatementRepository.php
new file mode 100644
index 0000000..9c76244
--- /dev/null
+++ b/src/Repository/AccountingStatementRepository.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Repository;
+
+use App\Entity\AccountingStatement;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<AccountingStatement>
+ *
+ * @method AccountingStatement|null find($id, $lockMode = null, $lockVersion = null)
+ * @method AccountingStatement|null findOneBy(array $criteria, array $orderBy = null)
+ * @method AccountingStatement[]    findAll()
+ * @method AccountingStatement[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
+ */
+class AccountingStatementRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, AccountingStatement::class);
+    }
+
+    //    /**
+    //     * @return AccountingStatement[] Returns an array of AccountingStatement objects
+    //     */
+    //    public function findByExampleField($value): array
+    //    {
+    //        return $this->createQueryBuilder('a')
+    //            ->andWhere('a.exampleField = :val')
+    //            ->setParameter('val', $value)
+    //            ->orderBy('a.id', 'ASC')
+    //            ->setMaxResults(10)
+    //            ->getQuery()
+    //            ->getResult()
+    //        ;
+    //    }
+
+    //    public function findOneBySomeField($value): ?AccountingStatement
+    //    {
+    //        return $this->createQueryBuilder('a')
+    //            ->andWhere('a.exampleField = :val')
+    //            ->setParameter('val', $value)
+    //            ->getQuery()
+    //            ->getOneOrNullResult()
+    //        ;
+    //    }
+}
diff --git a/src/Repository/AccountingTransactionRepository.php b/src/Repository/AccountingTransactionRepository.php
new file mode 100644
index 0000000..674c6a1
--- /dev/null
+++ b/src/Repository/AccountingTransactionRepository.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Repository;
+
+use App\Entity\AccountingTransaction;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<AccountingTransaction>
+ *
+ * @method AccountingTransaction|null find($id, $lockMode = null, $lockVersion = null)
+ * @method AccountingTransaction|null findOneBy(array $criteria, array $orderBy = null)
+ * @method AccountingTransaction[]    findAll()
+ * @method AccountingTransaction[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
+ */
+class AccountingTransactionRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, AccountingTransaction::class);
+    }
+
+    //    /**
+    //     * @return AccountingTransaction[] Returns an array of AccountingTransaction objects
+    //     */
+    //    public function findByExampleField($value): array
+    //    {
+    //        return $this->createQueryBuilder('t')
+    //            ->andWhere('t.exampleField = :val')
+    //            ->setParameter('val', $value)
+    //            ->orderBy('t.id', 'ASC')
+    //            ->setMaxResults(10)
+    //            ->getQuery()
+    //            ->getResult()
+    //        ;
+    //    }
+
+    //    public function findOneBySomeField($value): ?AccountingTransaction
+    //    {
+    //        return $this->createQueryBuilder('t')
+    //            ->andWhere('t.exampleField = :val')
+    //            ->setParameter('val', $value)
+    //            ->getQuery()
+    //            ->getOneOrNullResult()
+    //        ;
+    //    }
+}
diff --git a/src/Repository/TransactionRepository.php b/src/Repository/TipjarRepository.php
similarity index 59%
rename from src/Repository/TransactionRepository.php
rename to src/Repository/TipjarRepository.php
index d77f9af..86fa53b 100644
--- a/src/Repository/TransactionRepository.php
+++ b/src/Repository/TipjarRepository.php
@@ -2,27 +2,27 @@
 
 namespace App\Repository;
 
-use App\Entity\Transaction;
+use App\Entity\Tipjar;
 use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
 use Doctrine\Persistence\ManagerRegistry;
 
 /**
- * @extends ServiceEntityRepository<Transaction>
+ * @extends ServiceEntityRepository<Tipjar>
  *
- * @method Transaction|null find($id, $lockMode = null, $lockVersion = null)
- * @method Transaction|null findOneBy(array $criteria, array $orderBy = null)
- * @method Transaction[]    findAll()
- * @method Transaction[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
+ * @method Tipjar|null find($id, $lockMode = null, $lockVersion = null)
+ * @method Tipjar|null findOneBy(array $criteria, array $orderBy = null)
+ * @method Tipjar[]    findAll()
+ * @method Tipjar[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
  */
-class TransactionRepository extends ServiceEntityRepository
+class TipjarRepository extends ServiceEntityRepository
 {
     public function __construct(ManagerRegistry $registry)
     {
-        parent::__construct($registry, Transaction::class);
+        parent::__construct($registry, Tipjar::class);
     }
 
     //    /**
-    //     * @return Transaction[] Returns an array of Transaction objects
+    //     * @return Tipjar[] Returns an array of Tipjar objects
     //     */
     //    public function findByExampleField($value): array
     //    {
@@ -36,7 +36,7 @@ class TransactionRepository extends ServiceEntityRepository
     //        ;
     //    }
 
-    //    public function findOneBySomeField($value): ?Transaction
+    //    public function findOneBySomeField($value): ?Tipjar
     //    {
     //        return $this->createQueryBuilder('t')
     //            ->andWhere('t.exampleField = :val')
diff --git a/src/Service/ApiResourceNormalizer.php b/src/Service/ApiResourceNormalizer.php
index f8d958f..f615b99 100644
--- a/src/Service/ApiResourceNormalizer.php
+++ b/src/Service/ApiResourceNormalizer.php
@@ -14,7 +14,7 @@ class ApiResourceNormalizer
     {
         $classPieces = explode("\\", $className);
 
-        return strtolower(end($classPieces));
+        return lcfirst(end($classPieces));
     }
 
     /**
@@ -22,6 +22,6 @@ class ApiResourceNormalizer
      */
     public static function toEntity(string $resourceName): string
     {
-        return sprintf("App\\Entity\\%s", ucfirst(strtolower($resourceName)));
+        return sprintf("App\\Entity\\%s", ucfirst($resourceName));
     }
 }
diff --git a/src/Service/VersionedResourceService.php b/src/Service/VersionedResourceService.php
new file mode 100644
index 0000000..9fe8ed1
--- /dev/null
+++ b/src/Service/VersionedResourceService.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace App\Service;
+
+class VersionedResourceService
+{
+    public const VERSIONED_RESOURCES_DIR = 'versioned_resources';
+    public const VERSIONED_RESOURCE_NAMES_LOCK = 'versioned_resource_names_compiled.lock';
+
+    private static function getCompileDir(): string
+    {
+        return sprintf(
+            '%s%svar%s%s',
+            \dirname(__DIR__, 2),
+            DIRECTORY_SEPARATOR,
+            DIRECTORY_SEPARATOR,
+            self::VERSIONED_RESOURCES_DIR,
+        );
+    }
+
+    private static function getNamesLockFile(): string
+    {
+        return sprintf(
+            '%s%s%s',
+            self::getCompileDir(),
+            DIRECTORY_SEPARATOR,
+            self::VERSIONED_RESOURCE_NAMES_LOCK
+        );
+    }
+
+    /**
+     * Generates a directory for the service files.
+     */
+    public function makeCompileDir()
+    {
+        $compileDir = self::getCompileDir();
+
+        if (!\is_dir($compileDir)) {
+            \mkdir($compileDir, 0777, true);
+        }
+    }
+
+    /**
+     * Stores the given names in lock file.
+     * @param string[] $names
+     */
+    public function compileNames(array $names)
+    {
+        $this->makeCompileDir();
+
+        \file_put_contents(
+            self::getNamesLockFile(),
+            implode(PHP_EOL, $names)
+        );
+    }
+
+    /**
+     * @return array<string> List of the versioned resource names
+     * @see compileNames()
+     */
+    public static function getNames(): array
+    {
+        return explode(PHP_EOL, \file_get_contents(self::getNamesLockFile()));
+    }
+}
diff --git a/src/State/GatewayCheckoutProcessor.php b/src/State/GatewayCheckoutProcessor.php
index 006c97a..d907d8f 100644
--- a/src/State/GatewayCheckoutProcessor.php
+++ b/src/State/GatewayCheckoutProcessor.php
@@ -26,8 +26,6 @@ class GatewayCheckoutProcessor implements ProcessorInterface
         $this->entityManager->persist($data);
         $this->entityManager->flush();
 
-        $gateway->process($data);
-
-        return $data;
+        return $gateway->create($data);
     }
 }
diff --git a/src/State/GatewayCheckoutUpdateProcessor.php b/src/State/GatewayCheckoutUpdateProcessor.php
new file mode 100644
index 0000000..3ed4605
--- /dev/null
+++ b/src/State/GatewayCheckoutUpdateProcessor.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace App\State;
+
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProcessorInterface;
+use App\Dto\GatewayCheckoutUpdateDto;
+use App\Entity\GatewayCheckout;
+use App\Repository\GatewayCheckoutRepository;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\HttpException;
+
+class GatewayCheckoutUpdateProcessor implements ProcessorInterface
+{
+    public function __construct(
+        private GatewayCheckoutRepository $checkoutRepository,
+        private EntityManagerInterface $entityManager,
+    ) {
+    }
+
+    /**
+     * @param GatewayCheckoutUpdateDto $data
+     */
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): GatewayCheckout
+    {
+        $checkout = $this->checkoutRepository->find($uriVariables['id']);
+
+        if (!$checkout) {
+            throw new HttpException(Response::HTTP_NOT_FOUND, sprintf("The checkout '%s' does not exist.", $uriVariables['id']));
+        }
+
+        $checkout->setGatewayReference($data->gatewayReference);
+
+        $this->entityManager->persist($checkout);
+        $this->entityManager->flush();
+
+        return $checkout;
+    }
+}
diff --git a/src/State/VersionStateProvider.php b/src/State/ResourceVersionStateProvider.php
similarity index 79%
rename from src/State/VersionStateProvider.php
rename to src/State/ResourceVersionStateProvider.php
index cef0545..a14b3d6 100644
--- a/src/State/VersionStateProvider.php
+++ b/src/State/ResourceVersionStateProvider.php
@@ -8,11 +8,12 @@ use ApiPlatform\State\ProviderInterface;
 use App\ApiResource\Version;
 use App\Service\ApiResourceNormalizer;
 use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\Persistence\Mapping\MappingException;
 use Gedmo\Loggable\Entity\LogEntry;
 use Gedmo\Loggable\Entity\Repository\LogEntryRepository;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
-class VersionStateProvider implements ProviderInterface
+class ResourceVersionStateProvider implements ProviderInterface
 {
     private LogEntryRepository $versionRepository;
 
@@ -58,7 +59,16 @@ class VersionStateProvider implements ProviderInterface
     {
         $resourceClass = ApiResourceNormalizer::toEntity($resourceName);
 
-        $entity = $this->entityManager->find($resourceClass, $resourceId);
+        try {
+            $entity = $this->entityManager->find($resourceClass, $resourceId);
+        } catch (MappingException $e) {
+            throw new NotFoundHttpException(sprintf("Resource '%s' does not exist", $resourceName));
+        }
+
+        if (!$entity) {
+            throw new NotFoundHttpException(sprintf("Resource '%s' with ID '%s' not found", $resourceName, $resourceId));
+        }
+
         $logs = $this->versionRepository->getLogEntries($entity);
 
         $versions = [];
diff --git a/src/State/TransactionStateProcessor.php b/src/State/TransactionStateProcessor.php
deleted file mode 100644
index 342d6c7..0000000
--- a/src/State/TransactionStateProcessor.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-namespace App\State;
-
-use ApiPlatform\Metadata\Operation;
-use ApiPlatform\State\ProcessorInterface;
-use App\Entity\Transaction;
-use App\Library\Economy\Payment\GatewayLocator;
-use Doctrine\ORM\EntityManagerInterface;
-
-class TransactionStateProcessor implements ProcessorInterface
-{
-    public function __construct(
-        private GatewayLocator $gatewayLocator,
-        private EntityManagerInterface $entityManager
-    ) {
-    }
-
-    /**
-     * @param Transaction $data
-     */
-    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): Transaction
-    {
-        $gateway = $this->gatewayLocator->getGatewayOf($data);
-
-        $gateway->process($data);
-
-        return $data;
-    }
-}
diff --git a/tests/Library/Economy/Currency/EuropeanCentralBankExchangeTest.php b/tests/Library/Economy/Currency/EuropeanCentralBankExchangeTest.php
new file mode 100644
index 0000000..424adaf
--- /dev/null
+++ b/tests/Library/Economy/Currency/EuropeanCentralBankExchangeTest.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace App\Tests\Library\Economy\Currency;
+
+use App\Library\Economy\Currency\EuropeanCentralBankExchange;
+use PHPUnit\Framework\TestCase;
+
+class EuropeanCentralBankExchangeTest extends TestCase
+{
+    public function testGetsData()
+    {
+        $exchange = new EuropeanCentralBankExchange;
+        $exchangeData = $exchange->getData();
+
+        $this->assertIsArray($exchangeData);
+        $this->assertArrayHasKey('Cube', $exchangeData);
+        $this->assertArrayHasKey('@attributes', $exchangeData);
+    }
+
+    public function testStoresDataInApcuCache()
+    {
+        $exchange = new EuropeanCentralBankExchange;
+        // Data should be available on instantiation
+
+        $data = \apcu_fetch($exchange::ECB_DATA);
+
+        $this->assertNotFalse($data);
+
+        $exchangeData = \json_decode($data, true);
+        
+        $this->assertIsArray($exchangeData);
+        $this->assertArrayHasKey('Cube', $exchangeData);
+        $this->assertArrayHasKey('@attributes', $exchangeData);
+    }
+}