diff --git a/src/ApiResource/Gateway/CheckoutApiResource.php b/src/ApiResource/Gateway/CheckoutApiResource.php
index 6d48369..31f6f36 100644
--- a/src/ApiResource/Gateway/CheckoutApiResource.php
+++ b/src/ApiResource/Gateway/CheckoutApiResource.php
@@ -17,6 +17,7 @@ use App\Gateway\Tracking;
 use App\Mapping\Transformer\GatewayIdMapTransformer;
 use App\State\ApiResourceStateProvider;
 use App\State\Gateway\CheckoutStateProcessor;
+use App\Validator\ChargeToProjectInCampaign;
 use AutoMapper\Attribute\MapFrom;
 use AutoMapper\Attribute\MapTo;
 use Symfony\Component\Validator\Constraints as Assert;
@@ -70,6 +71,7 @@ class CheckoutApiResource
     #[API\ApiProperty(readableLink: true, writableLink: true)]
     #[Assert\NotBlank()]
     #[Assert\Count(min: 1)]
+    #[Assert\All([new ChargeToProjectInCampaign()])]
     public array $charges = [];
 
     /**
diff --git a/src/Dto/Gateway/CheckoutCreationDto.php b/src/Dto/Gateway/CheckoutCreationDto.php
index b13a963..7ab8980 100644
--- a/src/Dto/Gateway/CheckoutCreationDto.php
+++ b/src/Dto/Gateway/CheckoutCreationDto.php
@@ -8,6 +8,7 @@ use App\ApiResource\Gateway\GatewayApiResource;
 use App\Entity\Gateway\Checkout;
 use App\Gateway\RefundStrategy;
 use App\Mapping\Transformer\GatewayIdMapTransformer;
+use App\Validator\ChargeToProjectInCampaign;
 use AutoMapper\Attribute\MapFrom;
 use AutoMapper\Attribute\MapTo;
 use Symfony\Component\Validator\Constraints as Assert;
@@ -37,6 +38,7 @@ class CheckoutCreationDto
     #[API\ApiProperty(readableLink: true, writableLink: true)]
     #[Assert\NotBlank()]
     #[Assert\Count(min: 1)]
+    #[Assert\All([new ChargeToProjectInCampaign()])]
     public array $charges = [];
 
     /**
diff --git a/src/Validator/ChargeToProjectInCampaign.php b/src/Validator/ChargeToProjectInCampaign.php
new file mode 100644
index 0000000..b47b38f
--- /dev/null
+++ b/src/Validator/ChargeToProjectInCampaign.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Validator;
+
+use Symfony\Component\Validator\Constraint;
+
+#[\Attribute(\Attribute::TARGET_PROPERTY | \Attribute::TARGET_METHOD | \Attribute::IS_REPEATABLE)]
+final class ChargeToProjectInCampaign extends Constraint
+{
+    public string $message = 'The targeted Project {{ project }} behind Accounting {{ target }} is not in a status where it can receive Charges.';
+}
diff --git a/src/Validator/ChargeToProjectInCampaignValidator.php b/src/Validator/ChargeToProjectInCampaignValidator.php
new file mode 100644
index 0000000..74959d0
--- /dev/null
+++ b/src/Validator/ChargeToProjectInCampaignValidator.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace App\Validator;
+
+use App\ApiResource\Gateway\ChargeApiResource;
+use App\Dto\Gateway\ChargeCreationDto;
+use App\Entity\Accounting\Accounting;
+use App\Entity\Project\ProjectStatus;
+use App\Mapping\AutoMapper;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+final class ChargeToProjectInCampaignValidator extends ConstraintValidator
+{
+    public function __construct(
+        private AutoMapper $mapper,
+    ) {}
+
+    /**
+     * @param ChargeApiResource|ChargeCreationDto $value
+     * @param ChargeToProjectInCampaign           $constraint
+     */
+    public function validate(mixed $value, Constraint $constraint): void
+    {
+        if ($value === null || $value === '') {
+            return;
+        }
+
+        /** @var Accounting */
+        $target = $this->mapper->map($value->target, Accounting::class);
+
+        if ($target->getProject() === null) {
+            return;
+        }
+
+        if ($target->getProject()->getStatus() === ProjectStatus::InCampaign) {
+            return;
+        }
+
+        $this->context->buildViolation($constraint->message)
+            ->setParameter('{{ target }}', $value->target->id)
+            ->setParameter('{{ project }}', $target->getProject()->getId())
+            ->addViolation()
+        ;
+    }
+}