diff --git a/src/API/InvoiceController.php b/src/API/InvoiceController.php
index f7dd6717..a8b7830c 100644
--- a/src/API/InvoiceController.php
+++ b/src/API/InvoiceController.php
@@ -18,6 +18,7 @@ use FOS\RestBundle\Request\ParamFetcherInterface;
 use FOS\RestBundle\View\View;
 use FOS\RestBundle\View\ViewHandlerInterface;
 use OpenApi\Attributes as OA;
+use Symfony\Component\ExpressionLanguage\Expression;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Attribute\Route;
 use Symfony\Component\Security\Http\Attribute\IsGranted;
@@ -76,6 +77,9 @@ final class InvoiceController extends BaseApiController
         /** @var array<int> $customers */
         $customers = $paramFetcher->get('customers');
         foreach ($customerRepository->findByIds(array_unique($customers)) as $customer) {
+            if (!$this->isGranted('access', $customer)) {
+                throw $this->createAccessDeniedException('Cannot access Customer: ' . $customer->getId());
+            }
             $query->addCustomer($customer);
         }
 
@@ -90,6 +94,7 @@ final class InvoiceController extends BaseApiController
      * Fetch invoice
      */
     #[IsGranted('view_invoice')]
+    #[IsGranted(new Expression("is_granted('access', subject.getCustomer())"), 'invoice')]
     #[OA\Response(response: 200, description: 'Returns one invoice', content: new OA\JsonContent(ref: '#/components/schemas/Invoice'))]
     #[Route(methods: ['GET'], path: '/{id}', name: 'get_invoice', requirements: ['id' => '\d+'])]
     public function getAction(Invoice $invoice): Response
diff --git a/tests/API/InvoiceControllerTest.php b/tests/API/InvoiceControllerTest.php
index e83b2d8b..bf1d8aff 100644
--- a/tests/API/InvoiceControllerTest.php
+++ b/tests/API/InvoiceControllerTest.php
@@ -9,8 +9,11 @@
 
 namespace App\Tests\API;
 
+use App\Entity\Customer;
 use App\Entity\Invoice;
+use App\Entity\Team;
 use App\Entity\User;
+use App\Repository\TeamRepository;
 use App\Tests\DataFixtures\InvoiceFixtures;
 use PHPUnit\Framework\Attributes\Group;
 
@@ -123,4 +126,59 @@ class InvoiceControllerTest extends APIControllerBaseTestCase
     {
         $this->assertEntityNotFound(User::ROLE_USER, '/api/invoices/' . PHP_INT_MAX);
     }
+
+    public function testDownloadRespectsCustomerPermission(): void
+    {
+        $client = $this->getClientForAuthenticatedUser(User::ROLE_TEAMLEAD);
+
+        $invoices = $this->importInvoiceFixtures(1, [Invoice::STATUS_NEW]);
+        $invoice = $invoices[0];
+        $customer = $invoice->getCustomer();
+        self::assertInstanceOf(Customer::class, $customer);
+
+        $this->assertAccessIsGranted($client, '/api/invoices/' . $invoice->getId());
+
+        $content = $client->getResponse()->getContent();
+        self::assertIsString($content);
+        $result = json_decode($content, true);
+
+        self::assertIsArray($result);
+        self::assertApiResponseTypeStructure('Invoice', $result);
+
+        $team = new Team('foo');
+        $team->addTeamlead($this->getUserByRole(User::ROLE_ADMIN));
+        $team->addCustomer($customer);
+
+        $em = $this->getEntityManager();
+        /** @var TeamRepository $repository */
+        $repository = $em->getRepository(Team::class);
+        $repository->saveTeam($team);
+
+        $this->assertApiAccessDenied($client, '/api/invoices/' . $invoice->getId());
+    }
+
+    public function testCollectionRespectsCustomerPermission(): void
+    {
+        $client = $this->getClientForAuthenticatedUser(User::ROLE_TEAMLEAD);
+
+        $invoices = $this->importInvoiceFixtures(1, [Invoice::STATUS_NEW]);
+        $invoice = $invoices[0];
+        $customer = $invoice->getCustomer();
+        self::assertInstanceOf(Customer::class, $customer);
+
+        $query = ['customers' => [$customer->getId()]];
+        $this->assertAccessIsGranted($client, '/api/invoices', 'GET', $query);
+
+        $team = new Team('foo');
+        $team->addTeamlead($this->getUserByRole(User::ROLE_ADMIN));
+        $team->addCustomer($customer);
+
+        $em = $this->getEntityManager();
+        /** @var TeamRepository $repository */
+        $repository = $em->getRepository(Team::class);
+        $repository->saveTeam($team);
+
+        $this->request($client, '/api/invoices', 'GET', $query);
+        $this->assertApiResponseAccessDenied($client->getResponse());
+    }
 }