Tax type compound just add once.

app/Http/Controllers/Modals/Taxes.php

@@ -43,7 +43,13 @@ class Taxes extends Controller
 
         $rand = rand();
 
-        $html = view('modals.taxes.create', compact('types', 'tax_selector', 'rand'))->render();
+        $disable_options = [];
+
+        if ($compound = Tax::compound()->first()) {
+            $disable_options = ['compound'];
+        }
+
+        $html = view('modals.taxes.create', compact('types', 'tax_selector', 'disable_options', 'rand'))->render();
 
         return response()->json([
             'success' => true,

app/Http/Controllers/Settings/Taxes.php

@@ -57,7 +57,13 @@ class Taxes extends Controller
             'compound' => trans('taxes.compound'),
         ];
 
-        return view('settings.taxes.create', compact('types'));
+        $disable_options = [];
+
+        if ($compound = Tax::compound()->first()) {
+            $disable_options = ['compound'];
+        }
+
+        return view('settings.taxes.create', compact('types', 'disable_options'));
     }
 
     /**
@@ -105,7 +111,13 @@ class Taxes extends Controller
             'compound' => trans('taxes.compound'),
         ];
 
-        return view('settings.taxes.edit', compact('tax', 'types'));
+        $disable_options = [];
+
+        if ($tax->type != 'compound' && $compound = Tax::compound()->first()) {
+            $disable_options = ['compound'];
+        }
+
+        return view('settings.taxes.edit', compact('tax', 'types', 'disable_options'));
     }
 
     /**

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',
         ];
     }

public/css/custom.css

@@ -934,3 +934,8 @@ table .align-items-center td span.badge {
     border: none;
     color: #8898aa;
 }
+
+.el-select-dropdown__item.is-disabled {
+    color: #C0C4CC !important;
+    cursor: not-allowed !important;
+}

resources/views/settings/taxes/create.blade.php

@@ -21,7 +21,7 @@
 
                     {{ Form::textGroup('rate', trans('taxes.rate'), 'percent', ['@input' => 'onChangeTaxRate']) }}
 
-                    {{ Form::selectGroup('type', trans_choice('general.types', 1), 'bars', $types, 'normal') }}
+                    {{ Form::selectGroup('type', trans_choice('general.types', 1), 'bars', $types, 'normal', ['disabledOptions' => $disable_options]) }}
 
                     {{ Form::radioGroup('enabled', trans('general.enabled'), true) }}
                 </div>

resources/views/settings/taxes/edit.blade.php

@@ -22,7 +22,7 @@
 
                     {{ Form::textGroup('rate', trans('taxes.rate'), 'percent', ['@input' => 'onChangeTaxRate']) }}
 
-                    {{ Form::selectGroup('type', trans_choice('general.types', 1), 'bars', $types, $tax->type) }}
+                    {{ Form::selectGroup('type', trans_choice('general.types', 1), 'bars', $types, $tax->type, ['disabledOptions' => $disable_options]) }}
 
                     {{ Form::radioGroup('enabled', trans('general.enabled'), $tax->enabled) }}
                 </div>