diff --git a/services/nginx/app/routes/orderInvoicesRoute.php b/services/nginx/app/routes/orderInvoicesRoute.php
index 01da8864..ce227024 100644
--- a/services/nginx/app/routes/orderInvoicesRoute.php
+++ b/services/nginx/app/routes/orderInvoicesRoute.php
@@ -1816,6 +1816,7 @@ class orderInvoicesRoute
         $warnings = [];
         $invoice = (new collected_order_invoices_o())->select($collected_invoice_id);
         $invoice->requireSelected();
+        $this->requireCollectedInvoiceContextAccess($invoice);
 
         $draft_id = null;
         $booked_id = null;
@@ -1935,6 +1936,56 @@ class orderInvoicesRoute
         ];
     }
 
+    private function requireCollectedInvoiceContextAccess(collected_order_invoices_o $invoice): void
+    {
+        global $response;
+
+        if ($this->hasPermission('superuser')) {
+            return;
+        }
+
+        $invoice_customer_number = (int)$invoice->customer_number->value();
+        if ($invoice_customer_number > 0 && $this->isOwnCustomerContext($invoice_customer_number)) {
+            return;
+        }
+
+        if ($this->hasAccessToAllCollectedInvoiceDepartments((int)$invoice->id)) {
+            return;
+        }
+
+        $response->error('Permission denied for requested collected invoice.', 403);
+    }
+
+    private function hasAccessToAllCollectedInvoiceDepartments(int $collected_invoice_id): bool
+    {
+        $orders = new orders_o();
+        $order_departments = $orders->getFieldsWhere(
+            [
+                'invoice_collection_id' => $collected_invoice_id,
+                'deleted_at' => null,
+            ],
+            ['department_id']
+        );
+
+        $department_ids = array_values(array_unique(array_filter(array_map(static function (array $order): int {
+            return (int)($order['department_id'] ?? 0);
+        }, $order_departments), static function (int $department_id): bool {
+            return $department_id > 0;
+        })));
+
+        if (empty($department_ids)) {
+            return false;
+        }
+
+        foreach ($department_ids as $department_id) {
+            if (!$this->hasDepartmentAccess((string)$department_id)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     private function extractEconomicCustomerNumber(mixed $invoice_raw): ?int
     {
         if ($invoice_raw === null) {
diff --git a/services/nginx/app/tests/Unit/Invoicing/EconomicV2RouteAndVersioningHooksTest.php b/services/nginx/app/tests/Unit/Invoicing/EconomicV2RouteAndVersioningHooksTest.php
index edd28917..20bad8ef 100644
--- a/services/nginx/app/tests/Unit/Invoicing/EconomicV2RouteAndVersioningHooksTest.php
+++ b/services/nginx/app/tests/Unit/Invoicing/EconomicV2RouteAndVersioningHooksTest.php
@@ -77,3 +77,15 @@ it('keeps legacy compare endpoint path for backward compatibility', function ():
     expect($content)->toContain('/collected-invoices/economic/compare');
     expect($content)->toContain("requirePermission('compare_collected_invoice_economic')");
 });
+
+it('enforces customer or department context before building v2 invoice details payload', function (): void {
+    $routeFile = app_path('routes/orderInvoicesRoute.php');
+    $content = file_get_contents($routeFile);
+
+    expect($content)->not->toBeFalse();
+    expect($content)->toContain('private function requireCollectedInvoiceContextAccess');
+    expect($content)->toContain('$this->requireCollectedInvoiceContextAccess($invoice);');
+    expect($content)->toContain("$this->hasPermission('superuser')");
+    expect($content)->toContain('$this->isOwnCustomerContext($invoice_customer_number)');
+    expect($content)->toContain('$this->hasAccessToAllCollectedInvoiceDepartments((int)$invoice->id)');
+});