diff --git a/src/Gateway.php b/src/Gateway.php
index e5d9261..6edd1e8 100644
--- a/src/Gateway.php
+++ b/src/Gateway.php
@@ -44,7 +44,6 @@ public function getDefaultParameters()
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function purchase(array $options = [])
@@ -53,7 +52,6 @@ public function purchase(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function completePurchase(array $options = [])
@@ -62,7 +60,6 @@ public function completePurchase(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface|NotificationInterface
      */
     public function acceptNotification(array $options = [])
@@ -71,7 +68,6 @@ public function acceptNotification(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function fetchTransaction(array $options = [])
@@ -80,7 +76,6 @@ public function fetchTransaction(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function refund(array $options = [])
diff --git a/src/Message/FetchTransactionRequest.php b/src/Message/FetchTransactionRequest.php
index 83cb2c0..ebb5444 100644
--- a/src/Message/FetchTransactionRequest.php
+++ b/src/Message/FetchTransactionRequest.php
@@ -58,7 +58,6 @@ public function sendData($data)
     }
 
     /**
-     * @param $data
      * @return array
      *
      * @throws RtnException
diff --git a/src/Message/PurchaseRequest.php b/src/Message/PurchaseRequest.php
index efdc394..042e064 100644
--- a/src/Message/PurchaseRequest.php
+++ b/src/Message/PurchaseRequest.php
@@ -6,6 +6,7 @@
 use Omnipay\Common\Exception\InvalidRequestException;
 use Omnipay\Common\Message\AbstractRequest;
 use Omnipay\ECPay\Item;
+use Omnipay\ECPay\Traits\HasAmount;
 use Omnipay\ECPay\Traits\HasATMFields;
 use Omnipay\ECPay\Traits\HasATMOrCVSOrBARCODEFields;
 use Omnipay\ECPay\Traits\HasCreditFields;
@@ -32,6 +33,7 @@ class PurchaseRequest extends AbstractRequest
     use HasATMFields;
     use HasCVSOrBARCODEFields;
     use HasATMOrCVSOrBARCODEFields;
+    use HasAmount;
 
     protected $liveEndpoint = 'https://payment.ecpay.com.tw/Cashier/AioCheckOut/V5';
 
@@ -125,12 +127,14 @@ private function prepareItems()
         $currency = $this->getCurrency() ?: 'TWD';
 
         if (! $items) {
-            return [new Item([
-                'Name' => $this->getDescription(),
-                'Price' => $this->getAmount(),
-                'Currency' => $currency,
-                'Quantity' => 1,
-            ])];
+            return [
+                new Item([
+                    'Name' => $this->getDescription(),
+                    'Price' => $this->getAmount(),
+                    'Currency' => $currency,
+                    'Quantity' => 1,
+                ]),
+            ];
         }
 
         return array_map(static function ($item) use ($currency) {
diff --git a/src/Message/RefundRequest.php b/src/Message/RefundRequest.php
index 80379ec..2f1fd71 100644
--- a/src/Message/RefundRequest.php
+++ b/src/Message/RefundRequest.php
@@ -4,6 +4,7 @@
 
 use Ecpay\Sdk\Exceptions\RtnException;
 use Omnipay\Common\Message\AbstractRequest;
+use Omnipay\ECPay\Traits\HasAmount;
 use Omnipay\ECPay\Traits\HasDefaults;
 use Omnipay\ECPay\Traits\HasECPay;
 use Omnipay\ECPay\Traits\HasMerchantTradeNo;
@@ -15,6 +16,7 @@ class RefundRequest extends AbstractRequest
     use HasDefaults;
     use HasMerchantTradeNo;
     use HasTotalAmount;
+    use HasAmount;
 
     public function setTradeNo($value)
     {
diff --git a/src/Traits/HasAmount.php b/src/Traits/HasAmount.php
new file mode 100644
index 0000000..5c84dfc
--- /dev/null
+++ b/src/Traits/HasAmount.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Omnipay\ECPay\Traits;
+
+trait HasAmount
+{
+    public function getAmount()
+    {
+        return $this->getParameter('amount');
+    }
+}
diff --git a/tests/Message/AcceptNotificationRequestTest.php b/tests/Message/AcceptNotificationRequestTest.php
index 00833b0..75c382e 100644
--- a/tests/Message/AcceptNotificationRequestTest.php
+++ b/tests/Message/AcceptNotificationRequestTest.php
@@ -52,8 +52,6 @@ public function testGetData()
 
     /**
      * @depends testGetData
-     *
-     * @param $results
      */
     public function testSendData($results)
     {
diff --git a/tests/Message/CompletePurchaseRequestTest.php b/tests/Message/CompletePurchaseRequestTest.php
index c63243d..ee84c50 100644
--- a/tests/Message/CompletePurchaseRequestTest.php
+++ b/tests/Message/CompletePurchaseRequestTest.php
@@ -51,8 +51,6 @@ public function testGetData()
 
     /**
      * @depends testGetData
-     *
-     * @param $result
      */
     public function testSendData($result)
     {
diff --git a/tests/Message/FetchTransactionRequestTest.php b/tests/Message/FetchTransactionRequestTest.php
index cf80169..9cc3e82 100644
--- a/tests/Message/FetchTransactionRequestTest.php
+++ b/tests/Message/FetchTransactionRequestTest.php
@@ -35,8 +35,6 @@ public function testGetData()
 
     /**
      * @depends testGetData
-     *
-     * @param $result
      */
     public function testSendData($result)
     {
diff --git a/tests/Message/RefundRequestTest.php b/tests/Message/RefundRequestTest.php
index 0af50ea..e996139 100644
--- a/tests/Message/RefundRequestTest.php
+++ b/tests/Message/RefundRequestTest.php
@@ -22,7 +22,7 @@ public function testGetData()
             'MerchantTradeNo' => '2821567410556',
             'TradeNo' => '1909021549160081',
             'Action' => 'R',
-            'TotalAmount' => '1000.00',
+            'TotalAmount' => '1000',
         ], $request->getData());
     }
 }
diff --git a/tests/Message/VoidRequestTest.php b/tests/Message/VoidRequestTest.php
index d282ce1..7b24a74 100644
--- a/tests/Message/VoidRequestTest.php
+++ b/tests/Message/VoidRequestTest.php
@@ -22,7 +22,7 @@ public function testGetData()
             'MerchantTradeNo' => '2821567410556',
             'TradeNo' => '1909021549160081',
             'Action' => 'N',
-            'TotalAmount' => '1000.00',
+            'TotalAmount' => '1000',
         ], $request->getData());
     }
 }
diff --git a/tests/Stubs/StubGateway.php b/tests/Stubs/StubGateway.php
index c5007a5..f782a05 100644
--- a/tests/Stubs/StubGateway.php
+++ b/tests/Stubs/StubGateway.php
@@ -8,7 +8,6 @@
 class StubGateway extends Gateway
 {
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function fetchTransaction(array $options = [])
@@ -17,7 +16,6 @@ public function fetchTransaction(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function refund(array $options = [])
@@ -26,7 +24,6 @@ public function refund(array $options = [])
     }
 
     /**
-     * @param  array  $options
      * @return RequestInterface
      */
     public function void(array $options = [])