diff --git a/src/Transaction.php b/src/Transaction.php
index 1f9cc73..4f0aa40 100644
--- a/src/Transaction.php
+++ b/src/Transaction.php
@@ -12,6 +12,13 @@ class Transaction
 {
     use Gettable;
 
+    /**
+     * The errors for the transaction.
+     *
+     * @var array
+     */
+    protected $errors;
+
     /**
      * The Gateway instance.
      *
@@ -39,6 +46,16 @@ public function __construct(Gateway $gateway, array $params = [], $prepare = tru
         $this->params = $prepare ? $this->prepare($params) : $params;
     }
 
+    /**
+     * Check that the required parameters have not been provided to the transaction.
+     *
+     * @return bool
+     */
+    public function invalid()
+    {
+        return !$this->valid();
+    }
+
     /**
      * Prepare the transaction parameters.
      *
@@ -64,4 +81,38 @@ protected function prepare(array $params)
 
         return $params;
     }
+
+    /**
+     * Check that the required parameters have been provided to the transaction.
+     *
+     * @return bool
+     */
+    public function valid()
+    {
+        $params = $this->params;
+        $errors = [];
+
+        $errors[] = Validator::empty($params) ? 'No parameters provided.' : null;
+
+        if (isset($params['type'])) {
+            switch ($params['type']) {
+                case 'purchase':
+                    $errors[] = Validator::set($params, 'order_id') ? null : 'Order Id not provided.';
+                    $errors[] = Validator::set($params, 'pan') ? null : 'Credit card number not provided.';
+                    $errors[] = Validator::set($params, 'amount') ? null : 'Amount not provided.';
+                    $errors[] = Validator::set($params, 'expdate') ? null : 'Expiry date not provided.';
+
+                    break;
+                default:
+                    $errors[] = $params['type'].' is not a supported transaction type.';
+            }
+        } else {
+            $errors[] = 'Transaction type not provided.';
+        }
+
+        $errors = array_filter($errors);
+        $this->errors = $errors;
+
+        return empty($errors);
+    }
 }
\ No newline at end of file
diff --git a/src/Validator.php b/src/Validator.php
new file mode 100644
index 0000000..ff9bcd1
--- /dev/null
+++ b/src/Validator.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace CraigPaul\Moneris;
+
+class Validator
+{
+    /**
+     * @param array $array
+     *
+     * @return bool
+     */
+    public static function empty(array $array = [])
+    {
+        return empty($array);
+    }
+
+    /**
+     * @param array $array
+     * @param string $key
+     *
+     * @return bool
+     */
+    public static function set(array $array, string $key)
+    {
+        return isset($array[$key]);
+    }
+}
\ No newline at end of file