diff --git a/app/Helpers/StringHelpers.php b/app/Helpers/StringHelpers.php
index 87eca6d..231cd2a 100644
--- a/app/Helpers/StringHelpers.php
+++ b/app/Helpers/StringHelpers.php
@@ -1,18 +1,27 @@
 <?php
 
+use App\Enums\VoucherType;
 use Illuminate\Support\Number;
 use Illuminate\Support\Str;
 
 if (! function_exists('currency')) {
-    function currency(string $value, ?string $currency = null, ?string $locale = 'id_ID'): string
+    function currency(?string $value = null, ?string $currency = null, ?string $locale = 'id_ID'): string
     {
+        if ($value === null) {
+            return '';
+        }
+
         return $currency.Number::format($value, locale: $locale);
     }
 }
 
 if (! function_exists('replaceCurrency')) {
-    function replaceCurrency(string $value)
+    function replaceCurrency(?string $value = null)
     {
+        if ($value === null) {
+            return null;
+        }
+
         return (int) Str::replace('.', '', $value);
     }
 }
@@ -23,3 +32,12 @@ function percentage(int|float $value, int $precision = 2, int $maxPrecision = 2,
         return Number::percentage($value, $precision, $maxPrecision, $locale);
     }
 }
+
+if (! function_exists('formatDiscount')) {
+    function formatDiscount($amount, VoucherType $type, string $currency = 'Rp'): string
+    {
+        return $type === VoucherType::PERCENTAGE
+            ? percentage($amount)
+            : currency($amount, $currency);
+    }
+}