app/Filament/Resources/GrMasterResource.php

@@ -71,7 +71,12 @@ class GrMasterResource extends Resource
                 Forms\Components\TextInput::make('gr_number')
                     ->label('GR Number')
                     ->minLength(7)
-                    ->required(),
+                    ->required()
+                    ->rule(function (Get $get) {
+                        return Rule::unique('gr_masters', 'gr_number')
+                            ->where('plant_id', $get('plant_id'))
+                            ->ignore($get('id'));
+                    }),
                 Forms\Components\TextInput::make('serial_number')
                     ->label('Serial Number')
                     ->rule(function (callable $get) {