diff --git a/Admin/Install/db.json b/Admin/Install/db.json
index 3285f7b..c723fa6 100755
--- a/Admin/Install/db.json
+++ b/Admin/Install/db.json
@@ -225,7 +225,7 @@
             },
             "billing_bill_currency": {
                 "name": "billing_bill_currency",
-                "type": "INT",
+                "type": "VARCHAR(3)",
                 "null": false
             },
             "billing_bill_referral": {
diff --git a/Controller/ApiController.php b/Controller/ApiController.php
index d33b8f6..9880de9 100755
--- a/Controller/ApiController.php
+++ b/Controller/ApiController.php
@@ -120,15 +120,10 @@ final class ApiController extends Controller
     private function validateBillCreate(RequestAbstract $request) : array
     {
         $val = [];
-        /*if (($val['title'] = empty($request->getData('title')))
-            || ($val['plain'] = empty($request->getData('plain')))
-            || ($val['status'] = (
-                $request->getData('status') !== null
-                && !WikiStatus::isValidValue((int) $request->getData('status'))
-            ))
+        if (($val['client/customer'] = empty($request->getData('client') && empty($request->getData('supplier'))))
         ) {
             return $val;
-        }*/
+        }
 
         return [];
     }
@@ -292,6 +287,12 @@ final class ApiController extends Controller
 
         $pdf = $view->build();
 
+        if (!\is_file($pdfDir . $request->getData('bill') . '.pdf')) {
+            $response->header->status = RequestStatusCode::R_400;
+
+            return;
+        }
+
         $media = $this->app->moduleManager->get('Media')->createDbEntry(
             [
                 'status'    => UploadStatus::OK,
@@ -315,6 +316,8 @@ final class ApiController extends Controller
             $media->getId(),
             BillMapper::class, 'media', '', $request->getOrigin()
         );
+
+        $this->fillJsonResponse($request, $response, NotificationLevel::OK, 'PDF', 'Bill Pdf successfully created.', $media);
     }
 
     /**
diff --git a/Controller/BackendController.php b/Controller/BackendController.php
index 0efce49..792711a 100755
--- a/Controller/BackendController.php
+++ b/Controller/BackendController.php
@@ -121,6 +121,48 @@ final class BackendController extends Controller
         return $view;
     }
 
+    /**
+     * Routing end-point for application behaviour.
+     *
+     * @param RequestAbstract  $request  Request
+     * @param ResponseAbstract $response Response
+     * @param mixed            $data     Generic data
+     *
+     * @return RenderableInterface
+     *
+     * @since 1.0.0
+     * @codeCoverageIgnore
+     */
+    public function viewBillingPurchaseInvoiceCreate(RequestAbstract $request, ResponseAbstract $response, $data = null) : RenderableInterface
+    {
+        $view = new View($this->app->l11nManager, $request, $response);
+        $view->setTemplate('/Modules/Billing/Theme/Backend/invoice-create');
+        $view->addData('nav', $this->app->moduleManager->get('Navigation')->createNavigationMid(1005104001, $request, $response));
+
+        return $view;
+    }
+
+    /**
+     * Routing end-point for application behaviour.
+     *
+     * @param RequestAbstract  $request  Request
+     * @param ResponseAbstract $response Response
+     * @param mixed            $data     Generic data
+     *
+     * @return RenderableInterface
+     *
+     * @since 1.0.0
+     * @codeCoverageIgnore
+     */
+    public function viewBillingStockInvoiceCreate(RequestAbstract $request, ResponseAbstract $response, $data = null) : RenderableInterface
+    {
+        $view = new View($this->app->l11nManager, $request, $response);
+        $view->setTemplate('/Modules/Billing/Theme/Backend/invoice-create');
+        $view->addData('nav', $this->app->moduleManager->get('Navigation')->createNavigationMid(1005104001, $request, $response));
+
+        return $view;
+    }
+
     /**
      * Routing end-point for application behaviour.
      *
diff --git a/Models/Bill.php b/Models/Bill.php
index c7ed4ca..6e74dab 100755
--- a/Models/Bill.php
+++ b/Models/Bill.php
@@ -87,7 +87,7 @@ class Bill implements \JsonSerializable
      * @var null|\DateTime
      * @since 1.0.0
      */
-    private ?\DateTime $send = null;
+    public ?\DateTime $send = null;
 
     /**
      * Creator.
@@ -419,20 +419,6 @@ class Bill implements \JsonSerializable
         );
     }
 
-    /**
-     * Set Bill number.
-     *
-     * @param string $number Bill number
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setNumber(string $number) : void
-    {
-        $this->number = $number;
-    }
-
     /**
      * Get type
      *
@@ -485,394 +471,6 @@ class Bill implements \JsonSerializable
         $this->status = $status;
     }
 
-    /**
-     * Set shipping date.
-     *
-     * @param \DateTime $send Shipping date
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setSend(\DateTime $send) : void
-    {
-        $this->send = $send;
-    }
-
-    /**
-     * Get shipping date.
-     *
-     * @return null|\DateTime
-     *
-     * @since 1.0.0
-     */
-    public function getSend() : ?\DateTime
-    {
-        return $this->send;
-    }
-
-    /**
-     * Get client.
-     *
-     * @return mixed
-     *
-     * @since 1.0.0
-     */
-    public function getClient()
-    {
-        return $this->client;
-    }
-
-    /**
-     * Set client.
-     *
-     * @param mixed $client client
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setClient($client) : void
-    {
-        $this->client = $client;
-    }
-
-    /**
-     * Set shipping receiver.
-     *
-     * @param string $ship Shipping receiver
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipTo(string $ship) : void
-    {
-        $this->shipTo = $ship;
-    }
-
-    /**
-     * Get shipping receiver.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipTo() : string
-    {
-        return $this->shipTo;
-    }
-
-    /**
-     * Set shipping fao.
-     *
-     * @param string $ship FAO
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipFAO(string $ship) : void
-    {
-        $this->shipFAO = $ship;
-    }
-
-    /**
-     * Get shipping fao.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipFAO() : string
-    {
-        return $this->shipFAO;
-    }
-
-    /**
-     * Set shipping address.
-     *
-     * @param string $ship Shipping address
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipAddress(string $ship) : void
-    {
-        $this->shipAddress = $ship;
-    }
-
-    /**
-     * Get shipping address.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipAddress() : string
-    {
-        return $this->shipAddress;
-    }
-
-    /**
-     * Set shipping city.
-     *
-     * @param string $ship City
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipCity(string $ship) : void
-    {
-        $this->shipCity = $ship;
-    }
-
-    /**
-     * Get shipping city.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipCity() : string
-    {
-        return $this->shipCity;
-    }
-
-    /**
-     * Set shipping zip.
-     *
-     * @param string $ship Zip
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipZip(string $ship) : void
-    {
-        $this->shipZip = $ship;
-    }
-
-    /**
-     * Get shipping zip.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipZip() : string
-    {
-        return $this->shipZip;
-    }
-
-    /**
-     * Set shipping country.
-     *
-     * @param string $ship Country
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipCountry(string $ship) : void
-    {
-        $this->shipCountry = $ship;
-    }
-
-    /**
-     * Get shipping country.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShipCountry() : string
-    {
-        return $this->shipCountry;
-    }
-
-    /**
-     * Set billing receiver.
-     *
-     * @param string $bill Billing receiver
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillTo(string $bill) : void
-    {
-        $this->billTo = $bill;
-    }
-
-    /**
-     * Get billing receiver.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillTo() : string
-    {
-        return $this->billTo;
-    }
-
-    /**
-     * Set billing fao.
-     *
-     * @param string $bill FAO
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillFAO(string $bill) : void
-    {
-        $this->billFAO = $bill;
-    }
-
-    /**
-     * Get billing fao.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillFAO() : string
-    {
-        return $this->billFAO;
-    }
-
-    /**
-     * Set billing address.
-     *
-     * @param string $bill Billing address
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillAddress(string $bill) : void
-    {
-        $this->billAddress = $bill;
-    }
-
-    /**
-     * Get billing address.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillAddress() : string
-    {
-        return $this->billAddress;
-    }
-
-    /**
-     * Set billing city.
-     *
-     * @param string $bill City
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillCity(string $bill) : void
-    {
-        $this->billCity = $bill;
-    }
-
-    /**
-     * Get billing city.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillCity() : string
-    {
-        return $this->billCity;
-    }
-
-    /**
-     * Set billing zip.
-     *
-     * @param string $bill Zip
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillZip(string $bill) : void
-    {
-        $this->billZip = $bill;
-    }
-
-    /**
-     * Get billing zip.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillZip() : string
-    {
-        return $this->billZip;
-    }
-
-    /**
-     * Set billing country.
-     *
-     * @param string $bill Country
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillCountry(string $bill) : void
-    {
-        $this->billCountry = $bill;
-    }
-
-    /**
-     * Get billing country.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getBillCountry() : string
-    {
-        return $this->billCountry;
-    }
-
-    /**
-     * Get net amount.
-     *
-     * @return Money
-     *
-     * @since 1.0.0
-     */
-    public function getNet() : Money
-    {
-        return $this->net;
-    }
-
-    /**
-     * Get gross amount.
-     *
-     * @return Money
-     *
-     * @since 1.0.0
-     */
-    public function getGross() : Money
-    {
-        return $this->gross;
-    }
-
     /**
      * Set currency.
      *
@@ -899,162 +497,6 @@ class Bill implements \JsonSerializable
         return $this->currency;
     }
 
-    /**
-     * Set info.
-     *
-     * @param string $info Info
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setInfo(string $info) : void
-    {
-        $this->info = $info;
-    }
-
-    /**
-     * Get info.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getInfo() : string
-    {
-        return $this->info;
-    }
-
-    /**
-     * Set payment text.
-     *
-     * @param string $payment Payment text
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setPaymentText(string $payment) : void
-    {
-        $this->paymentText = $payment;
-    }
-
-    /**
-     * Get payment text.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getPaymentText() : string
-    {
-        return $this->paymentText;
-    }
-
-    /**
-     * Set shipping terms (e.g. inco).
-     *
-     * @param int $terms Terms
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setTerms(int $terms) : void
-    {
-        $this->terms = $terms;
-    }
-
-    /**
-     * Get terms.
-     *
-     * @return int
-     *
-     * @since 1.0.0
-     */
-    public function getTerms() : ?int
-    {
-        return $this->terms;
-    }
-
-    /**
-     * Set terms text.
-     *
-     * @param string $terms Terms text
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setTermsText(string $terms) : void
-    {
-        $this->termsText = $terms;
-    }
-
-    /**
-     * Get terms text.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getTermsText() : string
-    {
-        return $this->termsText;
-    }
-
-    /**
-     * Set shipping.
-     *
-     * @param int $shipping Shipping (e.g. incoterm)
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShipping(int $shipping) : void
-    {
-        $this->shipping = $shipping;
-    }
-
-    /**
-     * Get shipping.
-     *
-     * @return int
-     *
-     * @since 1.0.0
-     */
-    public function getShipping() : ?int
-    {
-        return $this->shipping;
-    }
-
-    /**
-     * Set shipping text.
-     *
-     * @param string $shipping Shipping text
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setShippingText(string $shipping) : void
-    {
-        $this->shippingText = $shipping;
-    }
-
-    /**
-     * Get shipping text.
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public function getShippingText() : string
-    {
-        return $this->shippingText;
-    }
-
     /**
      * Get vouchers.
      *
diff --git a/Models/BillElement.php b/Models/BillElement.php
index cd61756..ac17f62 100755
--- a/Models/BillElement.php
+++ b/Models/BillElement.php
@@ -119,42 +119,16 @@ class BillElement implements \JsonSerializable
         return $this->id;
     }
 
-    /**
-     * Set order.
-     *
-     * @param int $order Order
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setOrder(int $order) : void
-    {
-        $this->order = $order;
-    }
-
-    /**
-     * Get order.
-     *
-     * @return int
-     *
-     * @since 1.0.0
-     */
-    public function getOrder() : int
-    {
-        return $this->order;
-    }
-
     /**
      * Set item.
      *
-     * @param mixed $item Item
+     * @param int $item Item
      *
      * @return void
      *
      * @since 1.0.0
      */
-    public function setItem($item) : void
+    public function setItem(int $item) : void
     {
         $this->item = $item;
     }
diff --git a/Models/BillMapper.php b/Models/BillMapper.php
index 2530b08..b27e396 100755
--- a/Models/BillMapper.php
+++ b/Models/BillMapper.php
@@ -58,7 +58,7 @@ class BillMapper extends DataMapperAbstract
         'billing_bill_net'                     => ['name' => 'billing_bill_net',      'type' => 'Serializable',    'internal' => 'net'],
         'billing_bill_costs'                   => ['name' => 'billing_bill_costs',      'type' => 'Serializable',    'internal' => 'costs'],
         'billing_bill_profit'                  => ['name' => 'billing_bill_profit',      'type' => 'Serializable',    'internal' => 'profit'],
-        'billing_bill_currency'                => ['name' => 'billing_bill_currency',      'type' => 'int',    'internal' => 'currency'],
+        'billing_bill_currency'                => ['name' => 'billing_bill_currency',      'type' => 'string',    'internal' => 'currency'],
         'billing_bill_referral'                => ['name' => 'billing_bill_referral',      'type' => 'int',    'internal' => 'referral'],
         'billing_bill_referral_name'           => ['name' => 'billing_bill_referral_name',      'type' => 'string',    'internal' => 'referralName'],
         'billing_bill_reference'               => ['name' => 'billing_bill_reference',      'type' => 'int',    'internal' => 'reference'],
diff --git a/Models/BillTypeL11n.php b/Models/BillTypeL11n.php
index c8ba61c..76b9ff0 100755
--- a/Models/BillTypeL11n.php
+++ b/Models/BillTypeL11n.php
@@ -41,7 +41,7 @@ class BillTypeL11n implements \JsonSerializable, ArrayableInterface
      * @var int
      * @since 1.0.0
      */
-    protected int | BillType $type = 0;
+    public int | BillType $type = 0;
 
     /**
      * Language.
@@ -87,32 +87,6 @@ class BillTypeL11n implements \JsonSerializable, ArrayableInterface
         return $this->id;
     }
 
-    /**
-     * Set type.
-     *
-     * @param int $type Type id
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setBillType(int $type) : void
-    {
-        $this->type = $type;
-    }
-
-    /**
-     * Get type
-     *
-     * @return int
-     *
-     * @since 1.0.0
-     */
-    public function getType() : int | BillType
-    {
-        return $this->type;
-    }
-
     /**
      * Get language
      *
diff --git a/Models/NullBill.php b/Models/NullBill.php
index b644bbd..245111b 100755
--- a/Models/NullBill.php
+++ b/Models/NullBill.php
@@ -24,4 +24,16 @@ namespace Modules\Billing\Models;
  */
 final class NullBill extends Bill
 {
+	/**
+     * Constructor
+     *
+     * @param int $id Model id
+     *
+     * @since 1.0.0
+     */
+    public function __construct(int $id = 0)
+    {
+        $this->id = $id;
+        parent::__construct();
+    }
 }
diff --git a/info.json b/info.json
index 16374bc..02dd43f 100755
--- a/info.json
+++ b/info.json
@@ -20,7 +20,9 @@
         "Admin": "1.0.0",
         "Sales": "1.0.0",
         "Media": "1.0.0",
-        "ClientManagement": "1.0.0"
+        "ItemManagement": "1.0.0",
+        "ClientManagement": "1.0.0",
+        "SupplierManagement": "1.0.0"
     },
     "providing": {
         "Navigation": "*",
diff --git a/tests/Admin/AdminTest.php b/tests/Admin/AdminTest.php
new file mode 100644
index 0000000..496a52e
--- /dev/null
+++ b/tests/Admin/AdminTest.php
@@ -0,0 +1,27 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Admin;
+
+/**
+ * @internal
+ */
+class AdminTest extends \PHPUnit\Framework\TestCase
+{
+    protected const NAME = 'Billing';
+
+    protected const URI_LOAD = 'http://127.0.0.1/en/backend/admin/audit';
+
+    use \Modules\tests\ModuleTestTrait;
+}
diff --git a/tests/Controller/ApiControllerTest.php b/tests/Controller/ApiControllerTest.php
new file mode 100644
index 0000000..4b1d04a
--- /dev/null
+++ b/tests/Controller/ApiControllerTest.php
@@ -0,0 +1,181 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Controller;
+
+use Model\CoreSettings;
+use Modules\Admin\Models\AccountPermission;
+use Modules\Billing\Models\AuditMapper;
+use phpOMS\Account\Account;
+use phpOMS\Account\AccountManager;
+use phpOMS\Account\PermissionType;
+use phpOMS\Application\ApplicationAbstract;
+use phpOMS\Dispatcher\Dispatcher;
+use phpOMS\Event\EventManager;
+use phpOMS\Module\ModuleAbstract;
+use phpOMS\Module\ModuleManager;
+use phpOMS\Router\WebRouter;
+use phpOMS\Utils\TestUtils;
+use phpOMS\Message\Http\HttpRequest;
+use phpOMS\Message\Http\HttpResponse;
+use phpOMS\Message\Http\RequestStatusCode;
+use phpOMS\Uri\HttpUri;
+use phpOMS\Utils\RnG\DateTime;
+
+/**
+ * @testdox Modules\tests\Billing\Controller\ApiControllerTest: Billing api controller
+ *
+ * @internal
+ */
+class ApiControllerTest extends \PHPUnit\Framework\TestCase
+{
+    protected ApplicationAbstract $app;
+
+    /**
+     * @var \Modules\Billing\Controller\ApiController
+     */
+    protected ModuleAbstract $module;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp() : void
+    {
+        $this->app = new class() extends ApplicationAbstract
+        {
+            protected string $appName = 'Api';
+        };
+
+        $this->app->dbPool         = $GLOBALS['dbpool'];
+        $this->app->orgId          = 1;
+        $this->app->accountManager = new AccountManager($GLOBALS['session']);
+        $this->app->appSettings    = new CoreSettings();
+        $this->app->moduleManager  = new ModuleManager($this->app, __DIR__ . '/../../../../Modules/');
+        $this->app->dispatcher     = new Dispatcher($this->app);
+        $this->app->eventManager   = new EventManager($this->app->dispatcher);
+        $this->app->eventManager->importFromFile(__DIR__ . '/../../../../Web/Api/Hooks.php');
+
+        $account = new Account();
+        TestUtils::setMember($account, 'id', 1);
+
+        $permission = new AccountPermission();
+        $permission->setUnit(1);
+        $permission->setApp('backend');
+        $permission->setPermission(
+            PermissionType::READ
+            | PermissionType::CREATE
+            | PermissionType::MODIFY
+            | PermissionType::DELETE
+            | PermissionType::PERMISSION
+        );
+
+        $account->addPermission($permission);
+
+        $this->app->accountManager->add($account);
+        $this->app->router = new WebRouter();
+
+        $this->module = $this->app->moduleManager->get('Billing');
+
+        TestUtils::setMember($this->module, 'app', $this->app);
+    }
+
+    /**
+     * Tests bill, bill element and bill pdf archive create
+     *
+     * @covers Modules\Billing\Controller\ApiController
+     * @group module
+     */
+    public function testBillCreate() : void
+    {
+        $response = new HttpResponse();
+        $request  = new HttpRequest(new HttpUri(''));
+
+        $request->header->account = 1;
+
+        $request->setData('client', 1);
+        $request->setData('address', null);
+        $request->setData('type', 1);
+        $request->setData('status', null); // null = system settings, value = individual input
+        $request->setData('performancedate', DateTime::generateDateTime(new \DateTime('2015-01-01'), new \DateTime('now'))->format('Y-m-d H:i:s'));
+        $request->setData('sales_referral', null); // who these sales belong to
+        $request->setData('shipping_terms', 1); // e.g. incoterms
+        $request->setData('shipping_type', 1);
+        $request->setData('shipping_cost', null);
+        $request->setData('insurance_type', 1);
+        $request->setData('insurance_cost', null); // null = system settings, value = individual input
+        $request->setData('info', null); // null = system settings, value = individual input
+        $request->setData('currency', null); // null = system settings, value = individual input
+        $request->setData('payment', null); // null = system settings, value = individual input
+        $request->setData('payment_terms', null); // null = system settings, value = individual input
+
+        $this->module->apiBillCreate($request, $response);
+
+        $bId = $response->get('')['response']->getId();
+        self::assertGreaterThan(0, $bId);
+
+        for ($k = 0; $k < 10; ++$k) {
+            $response = new HttpResponse();
+            $request  = new HttpRequest(new HttpUri(''));
+
+            $request->header->account = 1;
+
+            $iId = \mt_rand(0, 10);
+
+            $request->setData('bill', $bId);
+            $request->setData('item', $iId === 0 ? null : $iId);
+
+            if ($iId === 0) {
+                // @todo: add text
+            }
+
+            $request->setData('quantity', \mt_rand(1, 11));
+            $request->setData('tax', null);
+            $request->setData('text', $iId === 0 ? 'Some test text' : null);
+
+            // discounts
+            if (\mt_rand(1, 100) < 31) {
+                $request->setData('discount_percentage', \mt_rand(5, 30));
+            }
+
+            $this->module->apiBillElementCreate($request, $response);
+            self::assertGreaterThan(0, $response->get('')['response']->getId());
+        }
+
+        $response = new HttpResponse();
+        $request  = new HttpRequest(new HttpUri(''));
+
+        $request->header->account = 1;
+        $request->setData('bill', $bId);
+
+        $this->module->apiBillPdfArchiveCreate($request, $response);
+
+        $result = $response->get('');
+        self::assertGreaterThan(0, $result === null ? -1 : $result['response']?->getId());
+    }
+
+    /**
+     * @covers Modules\Billing\Controller\ApiController
+     * @group module
+     */
+    public function testBillCreateInvalidData() : void
+    {
+        $response = new HttpResponse();
+        $request  = new HttpRequest(new HttpUri(''));
+
+        $request->header->account = 1;
+
+        $this->module->apiBillCreate($request, $response);
+        self::assertEquals(RequestStatusCode::R_400, $response->header->status);
+    }
+}
diff --git a/tests/Models/BillElementTest.php b/tests/Models/BillElementTest.php
new file mode 100644
index 0000000..91d007f
--- /dev/null
+++ b/tests/Models/BillElementTest.php
@@ -0,0 +1,53 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\BillElement;
+use phpOMS\Localization\ISO4217CharEnum;
+
+/**
+ * @internal
+ */
+class BillElementTest extends \PHPUnit\Framework\TestCase
+{
+    private BillElement $element;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp() : void
+    {
+        $this->element = new BillElement();
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillElement
+     * @group module
+     */
+    public function testDefault() : void
+    {
+        self::assertEquals(0, $this->element->getId());
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->element->singleSalesPriceNet);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->element->totalSalesPriceNet);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->element->singlePurchasePriceNet);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->element->totalPurchasePriceNet);
+    }
+
+    public function testItemInputOutput() : void
+    {
+        $this->element->setItem(123);
+        self::assertEquals(123, $this->element->item);
+    }
+}
diff --git a/tests/Models/BillTest.php b/tests/Models/BillTest.php
new file mode 100644
index 0000000..db9e6cc
--- /dev/null
+++ b/tests/Models/BillTest.php
@@ -0,0 +1,142 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\Bill;
+use Modules\Billing\Models\BillStatus;
+use Modules\Billing\Models\BillType;
+use phpOMS\Localization\ISO4217CharEnum;
+
+/**
+ * @internal
+ */
+class BillTest extends \PHPUnit\Framework\TestCase
+{
+    private Bill $bill;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp() : void
+    {
+        $this->bill = new Bill();
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testDefault() : void
+    {
+        self::assertEquals(0, $this->bill->getId());
+        self::assertEquals('', $this->bill->number);
+        self::assertEquals('', $this->bill->referralName);
+        self::assertEquals('', $this->bill->info);
+        self::assertEquals(0, $this->bill->type);
+        self::assertInstanceOf('\DateTimeImmutable', $this->bill->createdAt);
+        self::assertInstanceOf('\DateTime', $this->bill->performanceDate);
+        self::assertEquals(null, $this->bill->send);
+        self::assertEquals(null, $this->bill->client);
+        self::assertEquals(null, $this->bill->supplier);
+        self::assertEquals([], $this->bill->getVouchers());
+        self::assertEquals([], $this->bill->getTrackings());
+
+        self::assertEquals('', $this->bill->shipTo);
+        self::assertEquals('', $this->bill->shipFAO);
+        self::assertEquals('', $this->bill->shipAddress);
+        self::assertEquals('', $this->bill->shipCity);
+        self::assertEquals('', $this->bill->shipZip);
+        self::assertEquals('', $this->bill->shipCountry);
+
+        self::assertEquals('', $this->bill->billTo);
+        self::assertEquals('', $this->bill->billFAO);
+        self::assertEquals('', $this->bill->billAddress);
+        self::assertEquals('', $this->bill->billCity);
+        self::assertEquals('', $this->bill->billZip);
+        self::assertEquals('', $this->bill->billCountry);
+
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->bill->net);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->bill->gross);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->bill->costs);
+        self::assertInstanceOf('\phpOMS\Localization\Money', $this->bill->profit);
+
+        self::assertEquals(0, $this->bill->payment);
+        self::assertEquals('', $this->bill->paymentText);
+        self::assertEquals(0, $this->bill->terms);
+        self::assertEquals('', $this->bill->termsText);
+        self::assertEquals(0, $this->bill->shipping);
+        self::assertEquals('', $this->bill->shippingText);
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testNumberRendering() : void
+    {
+        $this->bill->number = '{y}{m}{d}-{id}';
+        self::assertEquals(\date('Y') . \date('m') . \date('d') . '-0', $this->bill->getNumber());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testTypeInputOutput() : void
+    {
+        $this->bill->setType(new BillType());
+        self::assertInstanceOf('\Modules\Billing\Models\BillType', $this->bill->getType());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testStatusInputOutput() : void
+    {
+        $this->bill->setStatus(BillStatus::ACTIVE);
+        self::assertEquals(BillStatus::ACTIVE, $this->bill->getStatus());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testCurrencyInputOutput() : void
+    {
+        $this->bill->setCurrency(ISO4217CharEnum::_USD);
+        self::assertEquals(ISO4217CharEnum::_USD, $this->bill->getCurrency());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testVoucherInputOutput() : void
+    {
+        $this->bill->addVoucher('TEST');
+        self::assertEquals(['TEST'], $this->bill->getVouchers());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\Bill
+     * @group module
+     */
+    public function testTrackingInputOutput() : void
+    {
+        $this->bill->addTracking('TEST');
+        self::assertEquals(['TEST'], $this->bill->getTrackings());
+    }
+}
diff --git a/tests/Models/BillTypeL11nTest.php b/tests/Models/BillTypeL11nTest.php
new file mode 100644
index 0000000..65781f7
--- /dev/null
+++ b/tests/Models/BillTypeL11nTest.php
@@ -0,0 +1,88 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\BillTypeL11n;
+use phpOMS\Localization\ISO639x1Enum;
+
+/**
+ * @internal
+ */
+class BillTypeL11nTest extends \PHPUnit\Framework\TestCase
+{
+    private BillTypeL11n $l11n;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp() : void
+    {
+        $this->l11n = new BillTypeL11n();
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillTypeL11n
+     * @group module
+     */
+    public function testDefault() : void
+    {
+        self::assertEquals(0, $this->l11n->getId());
+        self::assertEquals('', $this->l11n->name);
+        self::assertEquals(0, $this->l11n->type);
+        self::assertEquals(ISO639x1Enum::_EN, $this->l11n->getLanguage());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillTypeL11n
+     * @group module
+     */
+    public function testNameInputOutput() : void
+    {
+        $this->l11n->name = 'TestName';
+        self::assertEquals('TestName', $this->l11n->name);
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillTypeL11n
+     * @group module
+     */
+    public function testLanguageInputOutput() : void
+    {
+        $this->l11n->setLanguage(ISO639x1Enum::_DE);
+        self::assertEquals(ISO639x1Enum::_DE, $this->l11n->getLanguage());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillTypeL11n
+     * @group module
+     */
+    public function testSerialize() : void
+    {
+        $this->l11n->name = 'Title';
+        $this->l11n->description = 'Description';
+        $this->l11n->type   = 2;
+        $this->l11n->setLanguage(ISO639x1Enum::_DE);
+
+        self::assertEquals(
+            [
+                'id'       => 0,
+                'name'    => 'Title',
+                'type'      => 2,
+                'language' => ISO639x1Enum::_DE,
+            ],
+            $this->l11n->jsonSerialize()
+        );
+    }
+}
diff --git a/tests/Models/BillTypeTest.php b/tests/Models/BillTypeTest.php
new file mode 100644
index 0000000..55fb931
--- /dev/null
+++ b/tests/Models/BillTypeTest.php
@@ -0,0 +1,57 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\BillType;
+use Modules\Billing\Models\BillTypeL11n;
+
+/**
+ * @internal
+ */
+class BillTypeTest extends \PHPUnit\Framework\TestCase
+{
+    private BillType $type;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function setUp() : void
+    {
+        $this->type = new BillType();
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillType
+     * @group module
+     */
+    public function testDefault() : void
+    {
+        self::assertEquals(0, $this->type->getId());
+        self::assertTrue($this->type->transferStock);
+    }
+
+    /**
+     * @covers Modules\Billing\Models\BillType
+     * @group module
+     */
+    public function testL11nInputOutput() : void
+    {
+        $this->type->setL11n('Test1');
+        self::assertEquals('Test1', $this->type->getL11n());
+
+        $this->type->setL11n(new BillTypeL11n(0, 'Test2'));
+        self::assertEquals('Test2', $this->type->getL11n());
+    }
+}
diff --git a/tests/Models/NullBill.php b/tests/Models/NullBill.php
new file mode 100644
index 0000000..6697334
--- /dev/null
+++ b/tests/Models/NullBill.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBill;
+
+/**
+ * @internal
+ */
+final class Null extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBill
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\Bill', new NullBill());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBill
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBill(2);
+        self::assertEquals(2, $null->getId());
+    }
+}
diff --git a/tests/Models/NullBillElement.php b/tests/Models/NullBillElement.php
new file mode 100644
index 0000000..ecf1267
--- /dev/null
+++ b/tests/Models/NullBillElement.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBillElement;
+
+/**
+ * @internal
+ */
+final class Null extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBillElement
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\BillElement', new NullBillElement());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBillElement
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBillElement(2);
+        self::assertEquals(2, $null->getId());
+    }
+}
diff --git a/tests/Models/NullBillElementTest.php b/tests/Models/NullBillElementTest.php
new file mode 100644
index 0000000..6c9a130
--- /dev/null
+++ b/tests/Models/NullBillElementTest.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBillElement;
+
+/**
+ * @internal
+ */
+final class NullBillElementTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBillElement
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\BillElement', new NullBillElement());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBillElement
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBillElement(2);
+        self::assertEquals(2, $null->getId());
+    }
+}
diff --git a/tests/Models/NullBillTest.php b/tests/Models/NullBillTest.php
new file mode 100644
index 0000000..e466693
--- /dev/null
+++ b/tests/Models/NullBillTest.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBill;
+
+/**
+ * @internal
+ */
+final class NullBillTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBill
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\Bill', new NullBill());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBill
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBill(2);
+        self::assertEquals(2, $null->getId());
+    }
+}
diff --git a/tests/Models/NullBillType.php b/tests/Models/NullBillType.php
new file mode 100644
index 0000000..cd30551
--- /dev/null
+++ b/tests/Models/NullBillType.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBillType;
+
+/**
+ * @internal
+ */
+final class Null extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBillType
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\BillType', new NullBillType());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBillType
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBillType(2);
+        self::assertEquals(2, $null->getId());
+    }
+}
diff --git a/tests/Models/NullBillTypeTest.php b/tests/Models/NullBillTypeTest.php
new file mode 100644
index 0000000..6070dcf
--- /dev/null
+++ b/tests/Models/NullBillTypeTest.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 8.0
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 1.0
+ * @version   1.0.0
+ * @link      https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace Modules\Billing\tests\Models;
+
+use Modules\Billing\Models\NullBillType;
+
+/**
+ * @internal
+ */
+final class NullBillTypeTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\Billing\Models\NullBillType
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\Billing\Models\BillType', new NullBillType());
+    }
+
+    /**
+     * @covers Modules\Billing\Models\NullBillType
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullBillType(2);
+        self::assertEquals(2, $null->getId());
+    }
+}