diff --git a/Controller/ApiController.php b/Controller/ApiController.php
index b5a2c57..33839c8 100755
--- a/Controller/ApiController.php
+++ b/Controller/ApiController.php
@@ -227,7 +227,10 @@ final class ApiController extends Controller
     {
         $val = [];
         if (($val['client/supplier'] = (empty($request->getData('client'))
-            && (empty($request->getData('supplier')) && ((int) ($request->getData('supplier') ?? -1) !== 0))))
+                && (empty($request->getData('supplier'))
+                    && ((int) ($request->getData('supplier') ?? -1) !== 0)
+                )))
+            || ($val['type'] = (empty($request->getData('type'))))
         ) {
             return $val;
         }
diff --git a/Models/Bill.php b/Models/Bill.php
index fad8c9d..89041c0 100755
--- a/Models/Bill.php
+++ b/Models/Bill.php
@@ -61,10 +61,10 @@ class Bill implements \JsonSerializable
     /**
      * Bill type.
      *
-     * @var int|BillType
+     * @var BillType
      * @since 1.0.0
      */
-    public int | BillType $type = 0;
+    public BillType $type;
 
     /**
      * Bill status.
@@ -428,6 +428,7 @@ class Bill implements \JsonSerializable
         $this->performanceDate = new \DateTime();
         $this->createdBy       = new NullAccount();
         $this->referral        = new NullAccount();
+        $this->type            = new NullBillType();
     }
 
     /**
@@ -486,32 +487,6 @@ class Bill implements \JsonSerializable
         return $this->number;
     }
 
-    /**
-     * Get type
-     *
-     * @return int | BillType
-     *
-     * @since 1.0.0
-     */
-    public function getType() : int | BillType
-    {
-        return $this->type;
-    }
-
-    /**
-     * Set type
-     *
-     * @param int|BillType $type Type
-     *
-     * @return void
-     *
-     * @since 1.0.0
-     */
-    public function setType(int | BillType $type) : void
-    {
-        $this->type = $type;
-    }
-
     /**
      * Get status
      *
@@ -707,7 +682,7 @@ class Bill implements \JsonSerializable
     {
         $files = [];
         foreach ($this->media as $file) {
-            if ($file->type->getId() === $type) {
+            if ($file->type !== null && $file->type->getId() === $type) {
                 $files[] = $file;
             }
         }
diff --git a/Models/BillType.php b/Models/BillType.php
index 335374e..a2ff052 100755
--- a/Models/BillType.php
+++ b/Models/BillType.php
@@ -26,7 +26,7 @@ use phpOMS\Localization\ISO639x1Enum;
  * @link    https://karaka.app
  * @since   1.0.0
  */
-class BillType
+class BillType implements \JsonSerializable
 {
     /**
      * Id
@@ -108,4 +108,24 @@ class BillType
     {
         return $this->l11n instanceof BillTypeL11n ? $this->l11n->name : $this->l11n;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function toArray() : array
+    {
+        return [
+            'id'     => $this->id,
+            'numberFormat'   => $this->numberFormat,
+            'transferType'   => $this->transferType,
+        ];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return $this->toArray();
+    }
 }
diff --git a/tests/Models/BillTest.php b/tests/Models/BillTest.php
index 77c9d22..8db52ac 100755
--- a/tests/Models/BillTest.php
+++ b/tests/Models/BillTest.php
@@ -18,6 +18,7 @@ use Modules\Billing\Models\Bill;
 use Modules\Billing\Models\BillElement;
 use Modules\Billing\Models\BillStatus;
 use Modules\Billing\Models\BillType;
+use Modules\Billing\Models\NullBillType;
 use Modules\Media\Models\Media;
 use phpOMS\Localization\ISO4217CharEnum;
 
@@ -46,7 +47,7 @@ final class BillTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('', $this->bill->number);
         self::assertEquals('', $this->bill->referralName);
         self::assertEquals('', $this->bill->info);
-        self::assertEquals(0, $this->bill->type);
+        self::assertInstanceOf('\Modules\Billing\Models\NullBillType', $this->bill->type);
         self::assertInstanceOf('\DateTimeImmutable', $this->bill->createdAt);
         self::assertInstanceOf('\DateTime', $this->bill->performanceDate);
         self::assertNull($this->bill->send);
@@ -97,16 +98,6 @@ final class BillTest extends \PHPUnit\Framework\TestCase
         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
@@ -176,7 +167,7 @@ final class BillTest extends \PHPUnit\Framework\TestCase
     {
         $this->bill->number            = '123456';
         $this->bill->numberFormat      = '{y}';
-        $this->bill->type              = 2;
+        $this->bill->type              = new NullBillType(2);
         $this->bill->shipTo            = 'To';
         $this->bill->shipFAO           = 'FAO';
         $this->bill->shipAddress       = 'Address';
@@ -195,7 +186,7 @@ final class BillTest extends \PHPUnit\Framework\TestCase
                 'id'                => 0,
                 'number'            => '123456',
                 'numberFormat'      => '{y}',
-                'type'              => 2,
+                'type'              => $this->bill->type,
                 'shipTo'            => 'To',
                 'shipFAO'           => 'FAO',
                 'shipAddress'       => 'Address',