diff --git a/Controller/ApiController.php b/Controller/ApiController.php
index ad80ca6..a87ca51 100644
--- a/Controller/ApiController.php
+++ b/Controller/ApiController.php
@@ -24,12 +24,14 @@ use Modules\InvestmentManagement\Models\InvestmentMapper;
 use Modules\InvestmentManagement\Models\InvestmentObject;
 use Modules\InvestmentManagement\Models\InvestmentObjectMapper;
 use Modules\InvestmentManagement\Models\InvestmentStatus;
+use Modules\ItemManagement\Models\NullItem;
 use Modules\Media\Models\CollectionMapper;
 use Modules\Media\Models\MediaMapper;
 use Modules\Media\Models\NullMedia;
 use Modules\Media\Models\PathSettings;
 use Modules\Media\Models\Reference;
 use Modules\Media\Models\ReferenceMapper;
+use Modules\SupplierManagement\Models\NullSupplier;
 use phpOMS\Localization\BaseStringL11n;
 use phpOMS\Localization\BaseStringL11nType;
 use phpOMS\Localization\ISO639x1Enum;
@@ -478,9 +480,9 @@ final class ApiController extends Controller
         $investment->link         = $request->getDataString('link') ?? '';
         $investment->investment   = (int) $request->getData('investment');
         $investment->parent       = $request->getDataInt('parent');
-        $investment->supplier     = $request->getDataInt('supplier');
+        $investment->supplier     = $request->hasData('supplier') ? new NullSupplier((int) $request->getData('supplier')) : null;
         $investment->supplierName = $request->getDataString('suppliername') ?? '';
-        $investment->item         = $request->getDataInt('item');
+        $investment->item         = $request->hasData('item') ? new NullItem((int) $request->getData('item')) : null;
 
         // @todo reconsider the following lines. This seems rather complicated.
         if ($request->hasData('amount')) {
@@ -586,7 +588,6 @@ final class ApiController extends Controller
                 pathSettings: PathSettings::FILE_PATH
             );
 
-
             foreach ($uploaded as $media) {
                 $this->createModelRelation(
                     $request->header->account,
diff --git a/Models/AmountGroup.php b/Models/AmountGroup.php
index 59a29a6..9180aab 100644
--- a/Models/AmountGroup.php
+++ b/Models/AmountGroup.php
@@ -53,6 +53,13 @@ class AmountGroup
         $this->type = new BaseStringL11nType();
     }
 
+    /**
+     * Get sum of group
+     *
+     * @return FloatInt
+     *
+     * @since 1.0.0
+     */
     public function sum() : FloatInt
     {
         $sum = new FloatInt();
diff --git a/Models/InvestmentObject.php b/Models/InvestmentObject.php
index 3f7f566..26dabdc 100644
--- a/Models/InvestmentObject.php
+++ b/Models/InvestmentObject.php
@@ -57,6 +57,15 @@ class InvestmentObject
 
     public ?Item $item = null;
 
+    /**
+     * Get amount group by type name
+     *
+     * @param string $type Type name
+     *
+     * @return AmountGroup
+     *
+     * @since 1.0.0
+     */
     public function getAmountByTypeName(string $type) : AmountGroup
     {
         foreach ($this->amountGroups as $group) {
diff --git a/Theme/Backend/investment-option-view.tpl.php b/Theme/Backend/investment-option-view.tpl.php
index 1250c15..a12d06d 100644
--- a/Theme/Backend/investment-option-view.tpl.php
+++ b/Theme/Backend/investment-option-view.tpl.php
@@ -12,7 +12,6 @@
  */
 declare(strict_types=1);
 
-use Modules\InvestmentManagement\Models\InvestmentStatus;
 use phpOMS\Uri\UriFactory;
 
 /** @var \phpOMS\Views\View $this */