diff --git a/public/index.php b/public/index.php
index a97660f..fef6b00 100644
--- a/public/index.php
+++ b/public/index.php
@@ -95,6 +95,7 @@ $router->get('/invoices/{id}/book', fn($p) => (new InvoiceController())->book($p
 $router->post('/invoices/{id}/bookings', fn($p) => (new InvoiceController())->storeBooking($p));
 $router->post('/invoices/{id}/mark-paid', fn($p) => (new InvoiceController())->markPaid($p));
 $router->post('/invoices/{id}/cancel', fn($p) => (new InvoiceController())->cancel($p));
+$router->post('/invoices/{id}/delete', fn($p) => (new InvoiceController())->destroy($p));
 $router->post('/invoices/{id}/lines', fn($p) => (new InvoiceController())->addLine($p));
 $router->post('/invoices/{id}/lines/{line_id}/delete', fn($p) => (new InvoiceController())->deleteLine($p));
 
diff --git a/src/Controllers/InvoiceController.php b/src/Controllers/InvoiceController.php
index 556779f..686209e 100644
--- a/src/Controllers/InvoiceController.php
+++ b/src/Controllers/InvoiceController.php
@@ -17,19 +17,21 @@ class InvoiceController
 {
     public function index(array $params): void
     {
-        $filter = $_GET;
-        $page   = max(1, (int)($_GET['page'] ?? 1));
-        $result = Invoice::all($filter, $page);
+        $filter   = $_GET;
+        $page     = max(1, (int)($_GET['page'] ?? 1));
+        $result   = Invoice::all($filter, $page);
+        $settings = Setting::get();
 
         $view = new View();
         $view->render('layout/base.php', [
             'pageTitle'     => 'Ausgangsrechnungen',
             'content'       => $this->renderView('invoices/list', [
-                'rows'   => $result['rows'],
-                'total'  => $result['total'],
-                'pages'  => $result['pages'],
-                'page'   => $page,
-                'filter' => $filter,
+                'rows'     => $result['rows'],
+                'total'    => $result['total'],
+                'pages'    => $result['pages'],
+                'page'     => $page,
+                'filter'   => $filter,
+                'settings' => $settings,
             ]),
             'topbarActions' => '<a href="/invoices/new" class="btn btn-primary">+ Rechnung erstellen</a>',
         ]);
@@ -347,6 +349,17 @@ class InvoiceController
         return $belegNr;
     }
 
+    public function destroy(array $params): void
+    {
+        if (!Setting::isTestMode()) {
+            View::redirect('/invoices', 'Löschen ist nur im Testmodus erlaubt.', 'error');
+            return;
+        }
+        $id = (int)$params['id'];
+        Invoice::delete($id);
+        View::redirect('/invoices', 'Rechnung gelöscht.');
+    }
+
     public function markPaid(array $params): void
     {
         Invoice::markPaid((int)$params['id']);
diff --git a/src/Models/Invoice.php b/src/Models/Invoice.php
index 9dbe016..6396e0b 100644
--- a/src/Models/Invoice.php
+++ b/src/Models/Invoice.php
@@ -232,6 +232,19 @@ class Invoice
         );
     }
 
+    public static function delete(int $id): void
+    {
+        $invoice = self::find($id);
+        if (!$invoice) return;
+
+        if (!empty($invoice['beleg_id'])) {
+            Database::execute('DELETE FROM bookings WHERE beleg_id = ?', [$invoice['beleg_id']]);
+            Database::execute('DELETE FROM belege WHERE id = ?', [$invoice['beleg_id']]);
+        }
+        Database::execute('DELETE FROM invoice_lines WHERE invoice_id = ?', [$id]);
+        Database::execute('DELETE FROM invoices WHERE id = ?', [$id]);
+    }
+
     public static function generateRechnungsNr(): string
     {
         $settings = Database::fetchOne(
diff --git a/src/Views/invoices/list.php b/src/Views/invoices/list.php
index 571fd0d..3d79c5e 100644
--- a/src/Views/invoices/list.php
+++ b/src/Views/invoices/list.php
@@ -64,6 +64,12 @@
                             <?php if ($inv['status'] !== 'Entwurf'): ?>
                             <a href="/invoices/<?= $h($inv['id']) ?>/pdf" class="btn btn-secondary btn-sm">PDF</a>
                             <?php endif; ?>
+                            <?php if (!empty($settings['test_mode'])): ?>
+                            <form method="post" action="/invoices/<?= $h($inv['id']) ?>/delete" style="display:inline"
+                                  onsubmit="return confirm('Rechnung wirklich löschen?')">
+                                <button type="submit" class="btn btn-danger btn-sm">Löschen</button>
+                            </form>
+                            <?php endif; ?>
                         </div>
                     </td>
                 </tr>
diff --git a/tests/24_RechnungLoeschenTestmodusTest.php b/tests/24_RechnungLoeschenTestmodusTest.php
new file mode 100644
index 0000000..7eb4b9e
--- /dev/null
+++ b/tests/24_RechnungLoeschenTestmodusTest.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+use Steuerkram\Models\Customer;
+use Steuerkram\Models\Invoice;
+use Steuerkram\Models\Setting;
+
+class RechnungLoeschenTestmodusTest extends TestCase
+{
+    protected string $testName = 'Test 24: Rechnung löschen (nur im Testmodus)';
+
+    public function run(): void
+    {
+        $customerId = Customer::create([
+            'nachname' => 'LoeschTestKunde',
+            'strasse'  => 'Teststr. 1',
+            'plz'      => '12345',
+            'ort'      => 'Teststadt',
+            'land'     => 'DE',
+        ]);
+
+        $invoiceId = Invoice::create([
+            'customer_id'    => $customerId,
+            'betreff'        => 'Lösch-Test-Rechnung',
+            'rechnungs_datum' => date('Y-m-d'),
+            'lines'          => [
+                [
+                    'bezeichnung' => 'Testposition',
+                    'menge'       => 1,
+                    'einheit'     => 'Stk.',
+                    'einzelpreis' => 100,
+                    'ust_satz'    => 19,
+                ],
+            ],
+        ]);
+
+        $this->assertGreaterThan(0, $invoiceId, 'Rechnung wurde angelegt');
+        $invoice = Invoice::find($invoiceId);
+        $this->assert($invoice !== false, 'Rechnung per find() auffindbar');
+
+        // Rechnung löschen
+        Invoice::delete($invoiceId);
+
+        $afterDelete = Invoice::find($invoiceId);
+        $this->assert($afterDelete === false, 'Rechnung nach delete() nicht mehr auffindbar');
+
+        // Positionen ebenfalls gelöscht
+        $lines = Invoice::lines($invoiceId);
+        $this->assertEquals(0, count($lines), 'Invoice-Lines nach delete() gelöscht');
+
+        // test_mode-Flag ist bei Neuinstallation gesetzt
+        $settings = Setting::get();
+        $this->assert(isset($settings['test_mode']), 'test_mode-Feld in company_settings vorhanden');
+    }
+}