Tax type compound just add once.

app/Http/Requests/Setting/Tax.php

@@ -23,10 +23,25 @@ class Tax extends FormRequest
      */
     public function rules()
     {
+        // Check if store or update
+        if ($this->getMethod() == 'PATCH') {
+            $id = is_numeric($this->tax) ? $this->tax : $this->tax->getAttribute('id');
+        } else {
+            $id = null;
+        }
+
+        $company_id = $this->request->get('company_id');
+
+        $type = 'required|string';
+
+        if (!empty($this->request->get('type')) && $this->request->get('type') == 'compound') {
+            $type .= '|unique:taxes,NULL,' . $id . ',id,company_id,' . $company_id . ',type,compound,deleted_at,NULL';
+        }
+
         return [
             'name' => 'required|string',
             'rate' => 'required|min:0|max:100',
-            'type' => 'required|string',
+            'type' => $type,
             'enabled' => 'integer|boolean',
         ];
     }