diff --git a/src/Gateway.php b/src/Gateway.php
index fc73319..7f0ec0a 100644
--- a/src/Gateway.php
+++ b/src/Gateway.php
@@ -169,4 +169,31 @@ public function verify(array $params = [])
 
         return $this->process($transaction);
     }
+
+    /**
+     * Void a transaction.
+     *
+     * @param \CraigPaul\Moneris\Transaction|string $transaction
+     * @param string|null $order
+     *
+     * @return \CraigPaul\Moneris\Response
+     */
+    public function void($transaction, string $order = null)
+    {
+        if ($transaction instanceof Transaction) {
+            $order = $transaction->order();
+            $transaction = $transaction->number();
+        }
+
+        $params = [
+            'type' => 'purchasecorrection',
+            'crypt_type' => Crypt::SSL_ENABLED_MERCHANT,
+            'txn_number' => $transaction,
+            'order_id' => $order,
+        ];
+
+        $transaction = $this->transaction($params);
+
+        return $this->process($transaction);
+    }
 }
\ No newline at end of file
diff --git a/src/Transaction.php b/src/Transaction.php
index 01c2e40..076df9e 100644
--- a/src/Transaction.php
+++ b/src/Transaction.php
@@ -10,7 +10,7 @@
  * @property-read array $errors
  * @property-read \CraigPaul\Moneris\Gateway $gateway
  * @property-read array $params
- * @property SimpleXMLElement $response
+ * @property SimpleXMLElement|null $response
  */
 class Transaction
 {
@@ -38,9 +38,9 @@ class Transaction
     protected $params;
 
     /**
-     * @var SimpleXMLElement
+     * @var SimpleXMLElement|null
      */
-    protected $response;
+    protected $response = null;
 
     /**
      * Create a new Transaction instance.
@@ -64,6 +64,34 @@ public function invalid()
         return !$this->valid();
     }
 
+    /**
+     * Retrieve the transaction number, assuming the transaction has been processed.
+     *
+     * @return null|string
+     */
+    public function number()
+    {
+        if (is_null($this->response)) {
+            return null;
+        }
+
+        return (string)$this->response->receipt->TransID;
+    }
+
+    /**
+     * Retrieve the order id for the transaction. The is only available on certain transaction types.
+     *
+     * @return string|null
+     */
+    public function order()
+    {
+        if (isset($this->params['order_id'])) {
+            return $this->params['order_id'];
+        }
+
+        return null;
+    }
+
     /**
      * Prepare the transaction parameters.
      *
@@ -183,6 +211,11 @@ public function valid()
                         $errors[] = Validator::set($params, 'cvd') ? null : 'CVD not provided.';
                     }
 
+                    break;
+                case 'purchasecorrection':
+                    $errors[] = Validator::set($params, 'order_id') ? null : 'Order id not provided.';
+                    $errors[] = Validator::set($params, 'txn_number') ? null : 'Transaction number not provided.';
+
                     break;
                 default:
                     $errors[] = $params['type'].' is not a supported transaction type.';