diff --git a/src/ConstantsInterface.php b/src/ConstantsInterface.php
index e4efa7a0..9809e0af 100644
--- a/src/ConstantsInterface.php
+++ b/src/ConstantsInterface.php
@@ -115,6 +115,11 @@ interface ConstantsInterface
     const SERVICE_REPEAT            = 'repeat';
     const SERVICE_TOKEN             = 'directtoken';
     const SERVICE_DIRECT3D          = 'direct3dcallback';
+    const SERVICE_REST_MSK          = 'merchant-session-keys';
+    const SERVICE_REST_TRANSACTIONS = 'transactions';
+    const SERVICE_REST_INSTRUCTIONS = 'instructions';
+    const SERVICE_REST_3D           = '3d-secure';
+    const SERVICE_REST_3D_CHALLENGE = '3d-secure-challenge';
 
     /**
      * 0 = Do not send either customer or vendor emails
diff --git a/src/Message/AbstractRestRequest.php b/src/Message/AbstractRestRequest.php
new file mode 100644
index 00000000..8f83b875
--- /dev/null
+++ b/src/Message/AbstractRestRequest.php
@@ -0,0 +1,300 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay Abstract Rest Request.
+ * Base for Sage Pay Rest Server.
+ */
+use Omnipay\Common\Exception\InvalidRequestException;
+use Omnipay\SagePay\Extend\Item as ExtendItem;
+use Omnipay\SagePay\ConstantsInterface;
+use Psr\Http\Message\ResponseInterface;
+
+abstract class AbstractRestRequest extends AbstractRequest implements ConstantsInterface
+{
+
+    protected $VPSProtocol = '4.00';
+
+    /**
+     * @var string The service name, used in the endpoint URL.
+     */
+    protected $service;
+
+    /**
+     * @var string The protocol version number.
+     */
+    protected $apiVersion = 'v1';
+
+    protected $method = 'POST';
+
+    /**
+     * @var string Endpoint base URLs.
+     */
+    protected $liveEndpoint = 'https://pi-live.sagepay.com/api';
+    protected $testEndpoint = 'https://pi-test.sagepay.com/api';
+
+    public function getMethod()
+    {
+        return $this->method;
+    }
+
+    /**
+     * @return string URL for the test or live gateway, as appropriate.
+     */
+    public function getEndpoint()
+    {
+        return sprintf(
+            '%s/%s/%s',
+            $this->getTestMode() ? $this->testEndpoint : $this->liveEndpoint,
+            $this->getApiVersion(),
+            $this->isSubservice() ? $this->getSubService() : $this->getService()
+        );
+    }
+
+    public function isSubservice()
+    {
+        return !empty($this->getParentService());
+    }
+
+    /**
+     * The name of the service used in the endpoint to send the message.
+     * With override for services used on specific parent services
+     *
+     * @return string Sage Pay endpoint service name.
+     */
+    public function getSubService()
+    {
+        if ($this->isSubservice()) {
+            return sprintf(
+                '%s/%s/%s',
+                $this->getParentService(),
+                $this->getParentServiceReference(),
+                $this->getService()
+            );
+        }
+        return $this->getService();
+    }
+
+    public function getParentService()
+    {
+        return false;
+    }
+
+    public function getParentServiceReference()
+    {
+        return false;
+    }
+
+    /**
+     * Gets the api version for the end point.
+     *
+     * @return string
+     */
+    public function getApiVersion()
+    {
+        return $this->apiVersion;
+    }
+
+
+    public function getUsername()
+    {
+        return $this->getParameter('username');
+    }
+
+    public function setUsername($value)
+    {
+        return $this->setParameter('username', $value);
+    }
+
+    public function getPassword()
+    {
+        return $this->getParameter('password');
+    }
+
+    public function setPassword($value)
+    {
+        return $this->setParameter('password', $value);
+    }
+
+    public function getMerchantSessionKey()
+    {
+        return $this->getParameter('merchantSessionKey');
+    }
+
+    public function getCardIdentifier()
+    {
+        return $this->getParameter('cardIdentifier');
+    }
+
+    public function getTokenReusable()
+    {
+        return $this->getParameter('tokenReusable');
+    }
+
+    public function getTokenSave()
+    {
+        return $this->getParameter('tokenSave');
+    }
+
+    public function setTokenReusable($value)
+    {
+        return $this->setParameter('tokenReusable', $value);
+    }
+
+    public function setTokenSave($value)
+    {
+        return $this->setParameter('tokenSave', $value);
+    }
+
+    public function setMerchantSessionKey($value)
+    {
+        return $this->setParameter('merchantSessionKey', $value);
+    }
+
+    public function setCardIdentifier($value)
+    {
+        return $this->setParameter('cardIdentifier', $value);
+    }
+
+    /**
+     * Set the credentialType field(s).
+     *
+     * @param json $credentialType The credentialType for sagepay.
+     * @return $this
+     */
+    public function setCredentialType($credentialType)
+    {
+        return $this->setParameter('credentialType', $credentialType);
+    }
+
+    /**
+     * @return string The credentialType data as set.
+     */
+    public function getCredentialType()
+    {
+        return $this->getParameter('credentialType');
+    }
+
+    /**
+     * @return string
+     */
+    public function getMd()
+    {
+        return $this->getParameter('MD');
+    }
+
+    /**
+     * Override the MD passed into the current request.
+     *
+     * @param string $value
+     * @return $this
+     */
+    public function setMd($value)
+    {
+        return $this->setParameter('MD', $value);
+    }
+
+    /**
+     * Send data to the remote gateway, parse the result into an array,
+     * then use that to instantiate the response object.
+     *
+     * @param  array
+     * @return Response The reponse object initialised with the data returned from the gateway.
+     */
+    public function sendData($data)
+    {
+        // Issue #20 no data values should be null.
+
+        array_walk($data, function (&$value) {
+            if (! isset($value)) {
+                $value = '';
+            }
+        });
+
+        $httpResponse = $this
+            ->httpClient
+            ->request(
+                $this->getMethod(),
+                $this->getEndpoint(),
+                [
+                    'Content-Type' => 'application/json',
+                    'Authorization' => 'Basic '.base64_encode($this->getUsername() . ':' . $this->getPassword()),
+                ],
+                json_encode($data)
+            );
+
+        // We might want to check $httpResponse->getStatusCode()
+
+        $responseData = static::parseBodyData($httpResponse);
+
+        return $this->createResponse($responseData);
+    }
+
+    /**
+     * Add the billing address details to the data.
+     *
+     * @param array $data
+     * @return array $data
+     */
+    protected function getBillingAddressData(array $data = [])
+    {
+        $card = $this->getCard();
+
+        $data['customerFirstName'] = $card->getFirstName();
+        $data['customerLastName'] = $card->getLastName();
+        $data['billingAddress']['address1'] = $card->getBillingAddress1();
+        $data['billingAddress']['address2'] = $card->getBillingAddress2();
+        $data['billingAddress']['city'] = $card->getBillingCity();
+        $data['billingAddress']['postalCode'] = $card->getBillingPostcode();
+        $data['billingAddress']['state'] = $card->getBillingState();
+        $data['billingAddress']['country'] = $card->getBillingCountry();
+
+        if ($data['billingAddress']['country'] !== 'US') {
+            $data['billingAddress']['state'] = '';
+        }
+
+        return $data;
+    }
+
+    /**
+     * Add the shipping details to the data.
+     *
+     * @param array $data
+     * @return array $data
+     */
+    protected function getShippingDetailsData(array $data = [])
+    {
+        $card = $this->getCard();
+
+        $data['shippingDetails']['recipientFirstName'] = $card->getShippingFirstName();
+        $data['shippingDetails']['recipientLastName'] = $card->getShippingLastName();
+        $data['shippingDetails']['shippingAddress1'] = $card->getShippingAddress1();
+        $data['shippingDetails']['shippingAddress2'] = $card->getShippingAddress2();
+        $data['shippingDetails']['shippingCity'] = $card->getShippingCity();
+        $data['shippingDetails']['shippingPostalCode'] = $card->getShippingPostcode();
+        $data['shippingDetails']['shippingState'] = $card->getShippingState();
+        $data['shippingDetails']['shippingCountry'] = $card->getShippingCountry();
+
+        if ($data['shippingDetails']['shippingCountry'] !== 'US') {
+            $data['shippingDetails']['shippingState'] = '';
+        }
+
+        return $data;
+    }
+
+    /**
+     * The payload consists of json.
+     *
+     * @param ResponseInterface $httpResponse
+     * @return array
+     */
+    public static function parseBodyData(ResponseInterface $httpResponse)
+    {
+        $bodyText = (string)$httpResponse->getBody();
+
+        $responseData = json_decode($bodyText, true);
+
+        return $responseData;
+    }
+}
diff --git a/src/Message/DirectAuthorizeRequest.php b/src/Message/DirectAuthorizeRequest.php
index 19325f24..23b67891 100644
--- a/src/Message/DirectAuthorizeRequest.php
+++ b/src/Message/DirectAuthorizeRequest.php
@@ -9,7 +9,7 @@
 class DirectAuthorizeRequest extends AbstractRequest
 {
     /**
-     * @var array Some mapping from Omnipay card brand codes to Sage Pay card branc codes.
+     * @var array Some mapping from Omnipay card brand codes to Sage Pay card brand codes.
      */
     protected $cardBrandMap = array(
         'mastercard' => 'MC',
diff --git a/src/Message/RestResponse.php b/src/Message/RestResponse.php
new file mode 100644
index 00000000..a8bbb4e8
--- /dev/null
+++ b/src/Message/RestResponse.php
@@ -0,0 +1,145 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+use Omnipay\Common\Message\AbstractResponse;
+use Omnipay\Common\Message\RedirectResponseInterface;
+use Omnipay\Common\Message\RequestInterface;
+use Omnipay\SagePay\Traits\ResponseRestFieldsTrait;
+use Omnipay\SagePay\ConstantsInterface;
+
+/**
+ * Sage Pay Rest Response
+ */
+class RestResponse extends AbstractResponse implements RedirectResponseInterface, ConstantsInterface
+{
+    use ResponseRestFieldsTrait;
+
+    /**
+     * Gateway Reference
+     *
+     * Rest API - use just transactionId
+     *
+     * @return string.
+     */
+    public function getTransactionReference()
+    {
+        return $this->getDataItem('transactionId');
+    }
+
+    /**
+     * The only reason supported for a redirect from a Server transaction
+     * will be 3D Secure. PayPal may come into this at some point.
+     *
+     * @return bool True if a 3DSecure Redirect needs to be performed.
+     */
+    public function isRedirect()
+    {
+        return $this->getStatus() === static::SAGEPAY_STATUS_3DAUTH;
+    }
+
+    /**
+     * @return string URL to 3D Secure endpoint.
+     */
+    public function getRedirectUrl()
+    {
+        if ($this->isRedirect()) {
+            return $this->getDataItem('acsUrl');
+        }
+    }
+
+    /**
+     * @return string The redirect method.
+     */
+    public function getRedirectMethod()
+    {
+        return 'POST';
+    }
+
+    /**
+     * The usual reason for a redirect is for a 3D Secure check.
+     * Note: when PayPal is supported, a different set of data will be returned.
+     *
+     * @return array Collected 3D Secure POST data.
+     */
+    public function getRedirectData()
+    {
+        if ($this->isRedirect()) {
+            if ($this->getDataItem('cReq')) {
+                return array(
+                    'creq' => $this->getDataItem('cReq'),
+                    'threeDSSessionData' => $this->getRequest()->getMd(),
+                );
+            } else {
+                return array(
+                    'PaReq' => $this->getDataItem('paReq'),
+                    'TermUrl' => $this->getRequest()->getReturnUrl(),
+                    'MD' => $this->getRequest()->getMd(),
+                );
+            }
+        }
+    }
+
+    /**
+     * The Sage Pay ID to uniquely identify the transaction on their system.
+     * Only present if Status is OK or OK REPEATED.
+     *
+     * @return string
+     */
+    public function getVPSTxId()
+    {
+        return $this->getDataItem('VPSTxId');
+    }
+
+    /**
+     * A secret used to sign the notification request sent direct to your
+     * application.
+     */
+    public function getSecurityKey()
+    {
+        return $this->getDataItem('SecurityKey');
+    }
+
+    /**
+     * A secret used to sign the notification request sent direct to your
+     * application.
+     */
+    public function getErrors()
+    {
+        return $this->getDataItem('errors');
+    }
+
+    public function getError()
+    {
+        if (!empty($this->getErrors())) {
+            return array_values($this->getErrors())[0];
+        }
+        return null;
+    }
+
+    /**
+     * A secret used to sign the notification request sent direct to your
+     * application.
+     */
+    public function getErrorCode()
+    {
+        if ($this->getError()) {
+            $error = $this->getError();
+            return $error['code'] ?? null;
+        }
+        return $this->getCode();
+    }
+
+    /**
+     * A secret used to sign the notification request sent direct to your
+     * application.
+     */
+    public function getErrorDescription()
+    {
+        if ($this->getError()) {
+            $error = $this->getError();
+            return $error['description'] ?? null;
+        }
+        return $this->getMessage();
+    }
+}
diff --git a/src/Message/ServerRestCompletePurchaseRequest.php b/src/Message/ServerRestCompletePurchaseRequest.php
new file mode 100644
index 00000000..906a1fd4
--- /dev/null
+++ b/src/Message/ServerRestCompletePurchaseRequest.php
@@ -0,0 +1,103 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+use Omnipay\Common\Exception\InvalidResponseException;
+use Omnipay\SagePay\Message\ServerRestCompleteResponse;
+
+/**
+ * Sage Pay REST Complete Purchase Request.
+ */
+class ServerRestCompletePurchaseRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        if ($this->httpRequest->request->has('cres')) {
+            return static::SERVICE_REST_3D_CHALLENGE;
+        }
+
+        return static::SERVICE_REST_3D;
+    }
+
+    public function getParentService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS;
+    }
+
+    public function getParentServiceReference()
+    {
+        return $this->getParameter('transactionId');
+    }
+
+    public function getData()
+    {
+        if ($this->httpRequest->request->has('cres')) {
+            $data = array(
+                'cRes' => $this->httpRequest->request->get('cres'), // inconsistent caps are intentional
+                'MD' => $this->httpRequest->request->get('threeDSSessionData'),
+            );
+
+            if (empty($data['cRes']) || empty($data['MD'])) {
+                throw new InvalidResponseException;
+            }
+        } else {
+            $data = array(
+                'MD' => $this->getMd() ?: $this->httpRequest->request->get('MD'),
+                'paRes' => $this->getPaRes() ?: $this->httpRequest->request->get('PaRes'),
+            );
+
+            if (empty($data['MD']) || empty($data['paRes'])) {
+                throw new InvalidResponseException;
+            }
+        }
+
+        return $data;
+    }
+
+    /**
+     * @return string
+     */
+    public function getMd()
+    {
+        return $this->getParameter('MD');
+    }
+
+    /**
+     * Override the MD passed into the current request.
+     *
+     * @param string $value
+     * @return $this
+     */
+    public function setMd($value)
+    {
+        return $this->setParameter('MD', $value);
+    }
+
+    /**
+     * @return string
+     */
+    public function getPaRes()
+    {
+        return $this->getParameter('paRes');
+    }
+
+    /**
+     * Override the PaRes passed into the current request.
+     *
+     * @param string $value
+     * @return $this
+     */
+    public function setPaRes($value)
+    {
+        return $this->setParameter('paRes', $value);
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestCompleteResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestCompleteResponse($this, $data);
+    }
+}
diff --git a/src/Message/ServerRestCompleteResponse.php b/src/Message/ServerRestCompleteResponse.php
new file mode 100644
index 00000000..8b6bc13b
--- /dev/null
+++ b/src/Message/ServerRestCompleteResponse.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Complete Response
+ */
+class ServerRestCompleteResponse extends RestResponse
+{
+    /**
+     *
+     * @return bool false
+     */
+    public function isSuccessful()
+    {
+        return strtoupper($this->get3DSecureStatus() ?? $this->getStatus()) === static::SAGEPAY_STATUS_AUTHENTICATED;
+    }
+}
diff --git a/src/Message/ServerRestInstructionResponse.php b/src/Message/ServerRestInstructionResponse.php
new file mode 100644
index 00000000..b9cbfad2
--- /dev/null
+++ b/src/Message/ServerRestInstructionResponse.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Refund Response
+ */
+class ServerRestInstructionResponse extends RestResponse
+{
+    /**
+     *
+     * @return bool false
+     */
+    public function isSuccessful()
+    {
+        return $this->getInstructionType() ?? false;
+    }
+
+    /**
+     * @return string|null instructionType if present
+     */
+    public function getInstructionType()
+    {
+        return $this->getDataItem('instructionType');
+    }
+
+    /**
+     * @return string|null date if present
+     */
+    public function getInstructionDate()
+    {
+        return $this->getDataItem('date');
+    }
+}
diff --git a/src/Message/ServerRestMerchantSessionKeyRequest.php b/src/Message/ServerRestMerchantSessionKeyRequest.php
new file mode 100644
index 00000000..984c2063
--- /dev/null
+++ b/src/Message/ServerRestMerchantSessionKeyRequest.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Merchant Session Key Request
+ */
+class ServerRestMerchantSessionKeyRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        return static::SERVICE_REST_MSK;
+    }
+
+    /**
+     * Add the optional token details to the base data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        $data['vendorName'] = $this->getVendor();
+        $data['username'] = $this->getUsername();
+        $data['password'] = $this->getPassword();
+
+        return $data;
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestMerchantSessionKeyResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestMerchantSessionKeyResponse($this, $data);
+    }
+}
diff --git a/src/Message/ServerRestMerchantSessionKeyResponse.php b/src/Message/ServerRestMerchantSessionKeyResponse.php
new file mode 100644
index 00000000..539c3c3b
--- /dev/null
+++ b/src/Message/ServerRestMerchantSessionKeyResponse.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Merchant Session Key  Response
+ */
+class ServerRestMerchantSessionKeyResponse extends Response
+{
+    /**
+     * The initial Server response is never complete without
+     * redirecting the user.
+     *
+     * @return bool false
+     */
+    public function isSuccessful()
+    {
+        return $this->getMerchantSessionKey() ?? false;
+    }
+
+    /**
+     * @return string|null MSK if present
+     */
+    public function getMerchantSessionKey()
+    {
+        return $this->getDataItem('merchantSessionKey');
+    }
+}
diff --git a/src/Message/ServerRestPurchaseRequest.php b/src/Message/ServerRestPurchaseRequest.php
new file mode 100644
index 00000000..fbe7ca94
--- /dev/null
+++ b/src/Message/ServerRestPurchaseRequest.php
@@ -0,0 +1,117 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Purchase Request
+ */
+class ServerRestPurchaseRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS;
+    }
+
+    /**
+     * @return string the transaction type
+     */
+    public function getTxType()
+    {
+        return ucfirst(strtolower(static::TXTYPE_PAYMENT));
+    }
+
+    /**
+     * Add the optional token details to the base data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        $data = $this->getBasePurchaseData();
+
+        if ($this->getCardIdentifier() && $this->getMerchantSessionKey()) {
+            $data = $this->getPaymentMethodData($data);
+        }
+
+        return $data;
+    }
+
+    /**
+     * The required fields concerning the purchase
+     *
+     * @return array
+     */
+    protected function getBasePurchaseData()
+    {
+        $card = $this->getCard();
+
+        $data = $this->getBaseData();
+
+        $data['transactionType'] = $this->getTxType();
+        $data['vendorTxCode'] = $this->getTransactionId();
+        $data['description'] = $this->getDescription();
+        $data['amount'] = (int) $this->getAmount();
+        $data['currency'] = $this->getCurrency();
+        $data['NotificationURL'] = $this->getNotifyUrl() ?: $this->getReturnUrl();
+        $data['MD'] = $this->getMd();
+        $data['strongCustomerAuthentication'] = $this->getStrongCustomerAuthentication();
+        $data['credentialType'] = $this->getCredentialType();
+
+        $data = $this->getBillingAddressData($data);
+        $data = $this->getShippingDetailsData($data);
+
+        if ($card->getEmail()) {
+            $data['customerEmail'] = $card->getEmail();
+        }
+
+        // $data['ApplyAVSCV2'] = $this->getApplyAVSCV2() ?: static::APPLY_AVSCV2_DEFAULT;
+        $data['apply3DSecure'] = $this->getApply3DSecure() ?: static::APPLY_3DSECURE_APPLY;
+        // user parent data here and the abstract can provide txtype vendor etc
+        return $data;
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestPurchaseKeyResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestPurchaseResponse($this, $data);
+    }
+
+    /**
+     * @param array $data
+     * @return array $data.
+     */
+    public function getPaymentMethodData($data = [])
+    {
+        $data['paymentMethod']['card']['merchantSessionKey'] = $this->getMerchantSessionKey();
+        $data['paymentMethod']['card']['cardIdentifier'] = $this->getCardIdentifier();
+        if (!is_null($this->getTokenReusable())) {
+            $data['paymentMethod']['card']['reusable'] = $this->getTokenReusable();
+        }
+        if (!is_null($this->getTokenSave())) {
+            $data['paymentMethod']['card']['save'] = $this->getTokenSave();
+        }
+        return $data;
+    }
+
+    /**
+     * Set the strongCustomerAuthentication field(s).
+     *
+     * @param json $strongCustomerAuthentication The strongCustomerAuthentication for sagepay.
+     * @return $this
+     */
+    public function setStrongCustomerAuthentication($strongCustomerAuthentication)
+    {
+        return $this->setParameter('strongCustomerAuthentication', $strongCustomerAuthentication);
+    }
+
+    /**
+     * @return string The strongCustomerAuthentication data as set.
+     */
+    public function getStrongCustomerAuthentication()
+    {
+        return $this->getParameter('strongCustomerAuthentication');
+    }
+}
diff --git a/src/Message/ServerRestPurchaseResponse.php b/src/Message/ServerRestPurchaseResponse.php
new file mode 100644
index 00000000..dc61368e
--- /dev/null
+++ b/src/Message/ServerRestPurchaseResponse.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Purchase Response
+ */
+class ServerRestPurchaseResponse extends RestResponse
+{
+    //
+}
diff --git a/src/Message/ServerRestRefundRequest.php b/src/Message/ServerRestRefundRequest.php
new file mode 100644
index 00000000..815a3439
--- /dev/null
+++ b/src/Message/ServerRestRefundRequest.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+use Omnipay\SagePay\Message\ServerRestRefundResponse;
+
+/**
+ * Sage Pay REST Server Refund Request
+ */
+class ServerRestRefundRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS;
+    }
+
+    /**
+     * @return string the transaction type
+     */
+    public function getTxType()
+    {
+        return ucfirst(strtolower(static::TXTYPE_REFUND));
+    }
+
+    /**
+     * Add the optional token details to the base data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        $data = $this->getBaseData();
+
+        $data['transactionType'] = $this->getTxType();
+        $data['vendorTxCode'] = $this->getTransactionId();
+        $data['description'] = $this->getDescription();
+        $data['amount'] = (int) $this->getAmount();
+        // $data['currency'] = $this->getCurrency();
+        $data['referenceTransactionId'] = $this->getReferenceTransactionId();
+
+        return $data;
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestPurchaseKeyResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestRefundResponse($this, $data);
+    }
+
+    public function getReferenceTransactionId()
+    {
+        return $this->getParameter('referenceTransactionId');
+    }
+
+    public function setReferenceTransactionId($value)
+    {
+        return $this->setParameter('referenceTransactionId', $value);
+    }
+}
diff --git a/src/Message/ServerRestRefundResponse.php b/src/Message/ServerRestRefundResponse.php
new file mode 100644
index 00000000..fe57fb1f
--- /dev/null
+++ b/src/Message/ServerRestRefundResponse.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Refund Response
+ */
+class ServerRestRefundResponse extends RestResponse
+{
+    //
+}
diff --git a/src/Message/ServerRestRepeatRequest.php b/src/Message/ServerRestRepeatRequest.php
new file mode 100644
index 00000000..8559fdbd
--- /dev/null
+++ b/src/Message/ServerRestRepeatRequest.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+use Omnipay\SagePay\Message\ServerRestRepeatResponse;
+
+/**
+ * Sage Pay REST Server Repeat Request
+ */
+class ServerRestRepeatRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS;
+    }
+
+    /**
+     * @return string the transaction type
+     */
+    public function getTxType()
+    {
+        return ucfirst(strtolower(static::TXTYPE_REPEAT));
+    }
+
+    /**
+     * Add the optional token details to the base data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        $data = $this->getBaseData();
+
+        $data['transactionType'] = $this->getTxType();
+        $data['vendorTxCode'] = $this->getTransactionId();
+        $data['description'] = $this->getDescription();
+        $data['amount'] = (int) $this->getAmount();
+        $data['currency'] = $this->getCurrency();
+        $data['referenceTransactionId'] = $this->getReferenceTransactionId();
+        $data['credentialType'] = $this->getCredentialType();
+
+        return $data;
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestRepeatResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestRepeatResponse($this, $data);
+    }
+
+    public function getReferenceTransactionId()
+    {
+        return $this->getParameter('referenceTransactionId');
+    }
+
+    public function setReferenceTransactionId($value)
+    {
+        return $this->setParameter('referenceTransactionId', $value);
+    }
+}
diff --git a/src/Message/ServerRestRepeatResponse.php b/src/Message/ServerRestRepeatResponse.php
new file mode 100644
index 00000000..8c1d5e44
--- /dev/null
+++ b/src/Message/ServerRestRepeatResponse.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Repeat Response
+ */
+class ServerRestRepeatResponse extends RestResponse
+{
+    //
+}
diff --git a/src/Message/ServerRestRetrieveTransactionRequest.php b/src/Message/ServerRestRetrieveTransactionRequest.php
new file mode 100644
index 00000000..9f75536a
--- /dev/null
+++ b/src/Message/ServerRestRetrieveTransactionRequest.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Server Purchase Request
+ */
+class ServerRestRetrieveTransactionRequest extends AbstractRestRequest
+{
+    protected $method = 'GET';
+
+    public function getService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS. '/'.$this->getParameter('transactionId'); // temporary
+    }
+
+    /**
+     * Add the optional token details to the base data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        return [];
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestPurchaseKeyResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestRetrieveTransactionResponse($this, $data);
+    }
+
+    /**
+     * A card token is returned if one has been requested.
+     *
+     * @return string Currently an md5 format token.
+     */
+    public function getPaymentMethodData($data = [])
+    {
+        $data['paymentMethod']['card']['merchantSessionKey'] = $this->getMerchantSessionKey();
+        $data['paymentMethod']['card']['cardIdentifier'] = $this->getCardIdentifier();
+        return $data;
+    }
+}
diff --git a/src/Message/ServerRestRetrieveTransactionResponse.php b/src/Message/ServerRestRetrieveTransactionResponse.php
new file mode 100644
index 00000000..1ede91aa
--- /dev/null
+++ b/src/Message/ServerRestRetrieveTransactionResponse.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+/**
+ * Sage Pay REST Retrieve Transaction Response
+ */
+class ServerRestRetrieveTransactionResponse extends RestResponse
+{
+    //
+}
diff --git a/src/Message/ServerRestVoidRequest.php b/src/Message/ServerRestVoidRequest.php
new file mode 100644
index 00000000..0a2c77dc
--- /dev/null
+++ b/src/Message/ServerRestVoidRequest.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Omnipay\SagePay\Message;
+
+use Omnipay\SagePay\Message\ServerRestInstructionResponse;
+use Omnipay\SagePay\Message\ServerRestRefundResponse;
+
+/**
+ * Sage Pay REST Server Refund Request
+ */
+class ServerRestVoidRequest extends AbstractRestRequest
+{
+    public function getService()
+    {
+        return static::SERVICE_REST_INSTRUCTIONS;
+    }
+
+    public function getParentService()
+    {
+        return static::SERVICE_REST_TRANSACTIONS;
+    }
+
+    /**
+     * @return string the transaction type
+     */
+    public function getTxType()
+    {
+        return ucfirst(strtolower(static::TXTYPE_VOID));
+    }
+
+    /**
+     * Instruction data.
+     *
+     * @return array
+     */
+    public function getData()
+    {
+        $data = $this->getBaseData();
+
+        $data['instructionType'] = $this->getTxType();
+        return $data;
+    }
+
+    public function getParentServiceReference()
+    {
+        return $this->getParameter('transactionId');
+    }
+
+    /**
+     * @param array $data
+     * @return ServerRestInstructionResponse
+     */
+    protected function createResponse($data)
+    {
+        return $this->response = new ServerRestInstructionResponse($this, $data);
+    }
+}
diff --git a/src/RestServerGateway.php b/src/RestServerGateway.php
new file mode 100644
index 00000000..ec4b2337
--- /dev/null
+++ b/src/RestServerGateway.php
@@ -0,0 +1,106 @@
+<?php
+
+namespace Omnipay\SagePay;
+
+use Omnipay\SagePay\Message\ServerRestVoidRequest;
+use Omnipay\SagePay\Message\ServerRestRefundRequest;
+use Omnipay\SagePay\Message\ServerRestRepeatRequest;
+use Omnipay\SagePay\Message\ServerRestPurchaseRequest;
+use Omnipay\SagePay\Message\ServerRestCompletePurchaseRequest;
+use Omnipay\SagePay\Message\ServerRestMerchantSessionKeyRequest;
+use Omnipay\SagePay\Message\ServerRestRetrieveTransactionRequest;
+
+/**
+ * Sage Pay Rest Server Gateway
+ */
+class RestServerGateway extends ServerGateway
+{
+    public function getName()
+    {
+        return 'Sage Pay REST Server';
+    }
+
+    public function getUsername()
+    {
+        return $this->getParameter('username');
+    }
+
+    public function setUsername($value)
+    {
+        return $this->setParameter('username', $value);
+    }
+
+    public function getPassword()
+    {
+        return $this->getParameter('password');
+    }
+
+    public function setPassword($value)
+    {
+        return $this->setParameter('password', $value);
+    }
+
+    /**
+     * Create merchant session key (MSK).
+     */
+    public function createMerchantSessionKey(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestMerchantSessionKeyRequest::class, $parameters);
+    }
+
+    /**
+     * Purchase and handling of return from 3D Secure redirection.
+     */
+    public function purchase(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestPurchaseRequest::class, $parameters);
+    }
+
+    /**
+     * Handle purchase notifcation callback.
+     */
+    public function complete(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestCompletePurchaseRequest::class, $parameters);
+    }
+
+    /**
+     * Get transaction information from Sage.
+     */
+    public function getTransaction(array $parameters = [])
+    {
+        return $this->fetchTransaction($parameters);
+    }
+
+    /**
+     * Fetch transaction information from Sage.
+     */
+    public function fetchTransaction(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestRetrieveTransactionRequest::class, $parameters);
+    }
+
+    /**
+     * Refund request.
+     */
+    public function refund(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestRefundRequest::class, $parameters);
+    }
+
+    /**
+     * Repeat request.
+     */
+    public function repeat(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestRepeatRequest::class, $parameters);
+    }
+
+    /**
+     * Void request.
+     */
+    public function void(array $parameters = [])
+    {
+        return $this->createRequest(ServerRestVoidRequest::class, $parameters);
+    }
+}
diff --git a/src/Traits/ResponseRestFieldsTrait.php b/src/Traits/ResponseRestFieldsTrait.php
new file mode 100644
index 00000000..38198079
--- /dev/null
+++ b/src/Traits/ResponseRestFieldsTrait.php
@@ -0,0 +1,333 @@
+<?php
+
+namespace Omnipay\SagePay\Traits;
+
+/**
+ * Response fields shared between the Direct/Server response class and
+ * the notification handler.
+ */
+
+trait ResponseRestFieldsTrait
+{
+    /**
+     * Get a POST data item, or null if not present.
+     *
+     * @param  string $name    The key for the field.
+     * @param  mixed $default  The value to return if the data item is not found at all, or is null.
+     * @return mixed           The value of the field, often a string, but could be case to anything..
+     */
+    protected function getDataItem($name, $default = null)
+    {
+        $data = $this->getData();
+
+        return isset($this->data[$name]) ? $this->data[$name] : $default;
+    }
+
+    /**
+     * @return bool True if the transaction is successful and complete.
+     */
+    public function isSuccessful()
+    {
+        return $this->getStatus() === static::SAGEPAY_STATUS_OK
+            || $this->getStatus() === static::SAGEPAY_STATUS_OK_REPEATED
+            || $this->getStatus() === static::SAGEPAY_STATUS_REGISTERED
+            || $this->getStatus() === static::SAGEPAY_STATUS_AUTHENTICATED;
+    }
+
+    /**
+     * Get the cardReference generated when creating a card reference
+     * during an authorisation or payment, or as an explicit request.
+     *
+     * @return string Currently an md5 format token.
+     */
+    public function getCardReference()
+    {
+        return $this->getToken();
+    }
+
+    /**
+     * A card token is returned if one has been requested.
+     *
+     * @return string Currently an md5 format token.
+     */
+    public function getToken()
+    {
+        return $this->getDataItem('Token');
+    }
+
+    /**
+     * The raw status code.
+     *
+     * @return string One of static::SAGEPAY_STATUS_*
+     */
+    public function getStatus()
+    {
+        return strtoupper($this->getDataItem('status'));
+    }
+
+    /**
+     * The raw status code.
+     *
+     * @return string One of static::SAGEPAY_STATUS_*
+     */
+    public function getCode()
+    {
+        return $this->getStatusCode() ?? $this->getDataItem('code') ?? 'No Code';
+    }
+
+    /**
+     * The raw status code.
+     *
+     * @return string One of static::SAGEPAY_STATUS_*
+     */
+    public function getStatusCode()
+    {
+        return $this->getDataItem('statusCode');
+    }
+
+    /**
+     * Response Textual Message
+     *
+     * @return string A response message from the payment gateway
+     */
+    public function getMessage()
+    {
+        return $this->getStatusDetail() ?? $this->getDataItem('description');
+    }
+
+    /**
+     * Response Textual Message
+     *
+     * @return string A response message from the payment gateway
+     */
+    public function getStatusDetail()
+    {
+        return $this->getDataItem('statusDetail');
+    }
+
+    /**
+     * Sage Pay unique Authorisation Code for a successfully authorised transaction.
+     * Only present if Status is OK
+     *
+     * @return string
+     */
+    public function getTxAuthNo()
+    {
+        return $this->getRetrievalReference();
+    }
+
+    /**
+     * Sage Pay unique Authorisation Code for a successfully authorised transaction.
+     * Only present if Status is OK
+     *
+     * @return string
+     */
+    public function getRetrievalReference()
+    {
+        return $this->getDataItem('retrievalReference');
+    }
+
+    /**
+     * Sage Pay unique Authorisation Code for a successfully authorised transaction.
+     * Only present if Status is OK
+     *
+     * @return array
+     */
+    public function getAvsCvcCheck($wholeStatus = true)
+    {
+        $avsCvcCheck = $this->getDataItem('avsCvcCheck');
+
+        if (array_key_exists('status', $avsCvcCheck) && $wholeStatus) {
+            return $avsCvcCheck['status'];
+        }
+        return (object) $avsCvcCheck;
+    }
+
+    /**
+     * This is the response from AVS and CV2 checks.
+     * Provided for Vendor info and backward compatibility with the
+     * banks. Rules set up in MySagePay will accept or reject
+     * the transaction based on these values.
+     *
+     * More detailed results are split out in the next three fields:
+     * AddressResult, PostCodeResult and CV2Result.
+     *
+     * Not present if the Status is:
+     * 3DAUTH, AUTHENTICATED, PPREDIRECT or REGISTERED.
+     *
+     * @return string One of static::AVSCV2_RESULT_*
+     */
+    public function getAVSCV2()
+    {
+        return strtoupper($this->getAvsCvcCheck());
+    }
+
+    /**
+     * The specific result of the checks on the cardholder’s
+     * address numeric from the AVS/CV2 checks.
+     *
+     * @return string Once of static::ADDRESS_RESULT_*
+     */
+    public function getAddressResult()
+    {
+        return strtoupper($this->getAvsCvcCheck(false)->address);
+    }
+
+    /**
+     * The specific result of the checks on the cardholder’s
+     * Postcode from the AVS/CV2 checks.
+     *
+     * @return string Once of static::POSTCODE_RESULT_*
+     */
+    public function getPostCodeResult()
+    {
+        return strtoupper($this->getAvsCvcCheck(false)->postalCode);
+    }
+
+    /**
+     * The specific result of the checks on the cardholder’s CV2
+     * code from the AVS/CV2 checks.
+     *
+     * @return string One of static::CV2_RESULT_*
+     */
+    public function getCV2Result()
+    {
+        return strtoupper($this->getAvsCvcCheck(false)->securityCode);
+    }
+
+    /**
+     * This field details the results of the 3D-Secure checks
+     * where appropriate.
+     *
+     * @return string One of static::SECURE3D_STATUS_*
+     */
+    public function get3DSecureStatus()
+    {
+        $secure3DResponse = $this->getDataItem('3DSecure');
+
+        if (is_array($secure3DResponse) && array_key_exists('status', $secure3DResponse)) {
+            return strtoupper($secure3DResponse['status']);
+        }
+
+        return $secure3DResponse;
+    }
+
+    /**
+     * The encoded result code from the 3D-Secure checks (CAVV or UCAF).
+     * Only present if the 3DSecureStatus field is OK or ATTEMPTONLY.
+     *
+     * @return string Up to 32 characters long.
+     */
+    public function getCAVV()
+    {
+        return $this->getDataItem('CAVV');
+    }
+
+    /**
+     * The raw frawd response from the gateway.
+     *
+     * @return string One of static::FRAUD_RESPONSE_*
+     */
+    public function getFraudResponse()
+    {
+        return $this->getDataItem('FraudResponse');
+    }
+
+    /**
+     * The authorisation code returned from the bank. e.g. T99777
+     * @return string
+     */
+    public function getBankAuthCode()
+    {
+        return $this->getDataItem('BankAuthCode');
+    }
+
+    /**
+     * The decline code from the bank. These codes are
+     * specific to the bank. Please contact them for a description
+     * of each code. e.g. 00
+     * @return string Two digit code, specific to the bacnk.
+     */
+    public function getDeclineCode()
+    {
+        return $this->getDataItem('DeclineCode');
+    }
+
+    /**
+     * Returns the surcharge amount charged and is only
+     * present if a surcharge was applied to the transaction.
+     * The surcharge should be added to the original requested amount
+     * to give the total amount authorised for payment.
+     *
+     * @return string|null Contains a floating point number.
+     */
+    public function getSurcharge()
+    {
+        return $this->getDataItem('Surcharge');
+    }
+
+    /**
+     * Raw expiry date for the card, "MMYY" format by default.
+     * The expiry date is available for Sage Pay Direct responses, even if the
+     * remaining card details are not.
+     * Also supports custom formats.
+     *
+     * @param  string|null $format Format using the PHP date() format string.
+     * @return string
+     */
+    public function getExpiryDate($format = null)
+    {
+        $expiryDate = $this->getDataItem('ExpiryDate');
+
+        if ($format === null || $expiryDate === null) {
+            return $expiryDate;
+        } else {
+            return gmdate(
+                $format,
+                gmmktime(0, 0, 0, $this->getExpiryMonth(), 1, $this->getExpiryYear())
+            );
+        }
+    }
+
+    /**
+     * Get the card expiry month.
+     *
+     * @return int The month number, 1 to 12.
+     */
+    public function getExpiryMonth()
+    {
+        $expiryDate = $this->getDataItem('ExpiryDate');
+
+        if (! empty($expiryDate)) {
+            return (int)substr($expiryDate, 0, 2);
+        }
+    }
+
+    /**
+     * Get the card expiry year.
+     *
+     * @return int The full four-digit year.
+     */
+    public function getExpiryYear()
+    {
+        $expiryDate = $this->getDataItem('ExpiryDate');
+
+        if (! empty($expiryDate)) {
+            // COnvert 2-digit year to 4-dogot year, in 1970-2069 range.
+            $dateTime = \DateTime::createFromFormat('y', substr($expiryDate, 2, 2));
+            return (int)$dateTime->format('Y');
+        }
+    }
+
+    /**
+     * The transaction ID will be returned in the data for the Form API, or
+     * we will have to refer to the request for the Server and Direct APIs.
+     *
+     * @return @inherit
+     */
+    public function getTransactionId()
+    {
+        return $this->getDataItem('VendorTxCode')
+            ?: $this->getRequest()->getTransactionId();
+    }
+}