diff --git a/Layout/default/Preorder/Form.php b/Layout/default/Preorder/Form.php
index dd196cb49..8f48c2f16 100644
--- a/Layout/default/Preorder/Form.php
+++ b/Layout/default/Preorder/Form.php
@@ -293,9 +293,18 @@
                 </div>
               </div>
               
-              
-              
             </form>
+            
+            <?php if($preorder->submit_type == "api" && $preorder->submit_request): ?>
+              <div class="card">
+                <div class="card-body">
+                  <div class="form-group row">
+                    <label class="col-lg-2 col-form-label">Raw API Request</label>
+                    <div class="col-lg-10 text-monospace border" style="max-height: 512px; line-break: auto; overflow: auto; white-space: pre"><script>document.write(JSON.stringify(JSON.parse('<?=str_replace(["\n","\r"],"",$preorder->submit_request)?>'), null, "\t"));</script></div>
+                  </div>
+                </div>
+              </div>
+              <?php endif; ?>
           </div>
         </div>
         
diff --git a/Layout/default/Preordercampaign/Form.php b/Layout/default/Preordercampaign/Form.php
index dd7ddbf75..5fba33ed1 100644
--- a/Layout/default/Preordercampaign/Form.php
+++ b/Layout/default/Preordercampaign/Form.php
@@ -145,7 +145,7 @@
                   </div>
                   
                   <div class="form-group row">
-                    <label class="col-lg-2 col-form-label" for="district_is_city">Ortsteil ist Ort</label>
+                    <label class="col-lg-2 col-form-label" for="district_is_city">Ortsteil ist Ort:</label>
                     <div class="col-lg-10">
                       <select class="form-control" name="district_is_city" id="district_is_city">
                           <option value="0" <?=(!$campaign->district_is_city) ? "selected='selected'" : ""?>>Nein</option>
@@ -156,7 +156,7 @@
                   </div>
                   
                   <div class="form-group row">
-                    <label class="col-lg-2 col-form-label" for="hausnummer_add_zusatz">Adresszusatz an Hausnummer anhängen</label>
+                    <label class="col-lg-2 col-form-label" for="hausnummer_add_zusatz">Adresszusatz an Hausnummer anhängen:</label>
                     <div class="col-lg-10">
                       <select class="form-control" name="hausnummer_add_zusatz" id="hausnummer_add_zusatz">
                           <option value="0" <?=(!$campaign->hausnummer_add_zusatz) ? "selected='selected'" : ""?>>Nein</option>
@@ -165,6 +165,17 @@
                     </div>
                   </div>
                   
+                  <div class="form-group row">
+                    <label class="col-lg-2 col-form-label" for="exist_is_error">Erlaubte Vorbestellungen pro Wohneinheit (API):</label>
+                    <div class="col-lg-10">
+                      <select class="form-control" name="exist_is_error" id="exist_is_error">
+                          <option value="0" <?=(!$campaign->exist_is_error) ? "selected='selected'" : ""?>>Mehr als eine</option>
+                          <option value="1" <?=($campaign->exist_is_error) ? "selected='selected'" : ""?>>Maximal eine</option>
+                      </select>
+                      <small>Weiterer Bestellversuch liefert Fehler zurück</small>
+                    </div>
+                  </div>
+                  
                 </div>
               </div>
               
diff --git a/application/Api/v1/PreorderApicontroller.php b/application/Api/v1/PreorderApicontroller.php
index 45a26711a..85e35fb35 100644
--- a/application/Api/v1/PreorderApicontroller.php
+++ b/application/Api/v1/PreorderApicontroller.php
@@ -12,6 +12,7 @@ class PreorderApicontroller extends mfBaseApicontroller {
   private $allowed_preordertypes = [];
   private $district_is_city = false;
   private $hausnummer_add_zusatz = false;
+  private $exist_is_error = false;
   
   protected function init() {
     $db = $this->db(ADDRESSDB_DBHOST, ADDRESSDB_DBUSER, ADDRESSDB_DBPASS, ADDRESSDB_DBNAME);
@@ -47,10 +48,12 @@ class PreorderApicontroller extends mfBaseApicontroller {
         if($campaign->district_is_city == 1) {
           $this->district_is_city = true;
         }
-        
         if($campaign->hausnummer_add_zusatz == 1) {
           $this->hausnummer_add_zusatz = true;
         }
+        if($campaign->exist_is_error == 1) {
+          $this->exist_is_error = true;
+        }
         
       }
       
@@ -240,6 +243,19 @@ class PreorderApicontroller extends mfBaseApicontroller {
       }
     }
     
+    if($this->exist_is_error) {
+      /*
+       * check if there is an existing preorder for this unit already
+       */
+      if($unit) {
+        $existing_preorder = PreorderModel::getFirst(['adb_wohneinheit_id' => $unit->wohneinheit_id]);
+        if($existing_preorder) {
+          return mfResponse::Forbidden(['message' => "Für diese Wohneinheit liegt bereits eine Bestellung vor"]);
+        }
+      }
+    }
+    
+    
     $address_info = $this->db()->escape(trim($this->post['address_info']));
     
     // get correct campaign by salescluster
diff --git a/application/Preorder/PreorderModel.php b/application/Preorder/PreorderModel.php
index d37cd9756..b133fbb18 100644
--- a/application/Preorder/PreorderModel.php
+++ b/application/Preorder/PreorderModel.php
@@ -94,7 +94,7 @@ class PreorderModel {
     
   }
   
-  public static function getFirst() {
+  public static function getFirst($filter = false) {
     $db = FronkDB::singleton();
     
     $where = self::getSqlFilter($filter);
diff --git a/application/Preordercampaign/PreordercampaignController.php b/application/Preordercampaign/PreordercampaignController.php
index 90b77496e..0398a1800 100644
--- a/application/Preordercampaign/PreordercampaignController.php
+++ b/application/Preordercampaign/PreordercampaignController.php
@@ -249,6 +249,12 @@ class PreordercampaignController extends mfBaseController {
       $data['hausnummer_add_zusatz'] = 0;
     }
     
+    if($r->exist_is_error == 1) {
+      $data['exist_is_error'] = 1;
+    } else {
+      $data['exist_is_error'] = 0;
+    }
+    
     $data['edit_by'] = $this->me->id;
     
     if($mode == "add") {
diff --git a/application/Preordercampaign/PreordercampaignModel.php b/application/Preordercampaign/PreordercampaignModel.php
index 0a987781f..4b4f18976 100644
--- a/application/Preordercampaign/PreordercampaignModel.php
+++ b/application/Preordercampaign/PreordercampaignModel.php
@@ -13,6 +13,7 @@ class PreordercampaignModel {
   public $required_preorder_fields;
   public $district_is_city;
   public $hausnummer_add_zusatz;
+  public $exist_is_error;
   public $note;
   
   public $create_by;