diff --git a/src/Message/ExpressAuthorizeRequest.php b/src/Message/ExpressAuthorizeRequest.php
index e05f3bf..fd08b88 100644
--- a/src/Message/ExpressAuthorizeRequest.php
+++ b/src/Message/ExpressAuthorizeRequest.php
@@ -2,14 +2,86 @@
 
 namespace Omnipay\PayPal\Message;
 
+use Omnipay\Common\Exception\InvalidRequestException;
+use Omnipay\PayPal\Support\InstantUpdateApi\ShippingOption;
+
 /**
  * PayPal Express Authorize Request
  */
 class ExpressAuthorizeRequest extends AbstractRequest
 {
+
+    const DEFAULT_CALLBACK_TIMEOUT = 5;
+
+    public function setCallback($callback)
+    {
+        return $this->setParameter('callback', $callback);
+    }
+
+    public function getCallback()
+    {
+        return $this->getParameter('callback');
+    }
+
+    public function setCallbackTimeout($callbackTimeout)
+    {
+        return $this->setParameter('callbackTimeout', $callbackTimeout);
+    }
+
+    public function getCallbackTimeout()
+    {
+        return $this->getParameter('callbackTimeout');
+    }
+
+    /**
+     * @param ShippingOption[] $data
+     */
+    public function setShippingOptions($data)
+    {
+        $this->setParameter('shippingOptions', $data);
+    }
+
+    /**
+     * @return ShippingOption[]
+     */
+    public function getShippingOptions()
+    {
+        return $this->getParameter('shippingOptions');
+    }
+
+    protected function validateCallback()
+    {
+        $callback = $this->getCallback();
+
+        if (!empty($callback)) {
+            $shippingOptions = $this->getShippingOptions();
+
+            if (empty($shippingOptions)) {
+                throw new InvalidRequestException(
+                    'When setting a callback for the Instant Update API you must set shipping options'
+                );
+            } else {
+                $hasDefault = false;
+                foreach ($shippingOptions as $shippingOption) {
+                    if ($shippingOption->isDefault()) {
+                        $hasDefault = true;
+                        continue;
+                    }
+                }
+
+                if (!$hasDefault) {
+                    throw new InvalidRequestException(
+                        'One of the supplied shipping options must be set as default'
+                    );
+                }
+            }
+        }
+    }
+
     public function getData()
     {
         $this->validate('amount', 'returnUrl', 'cancelUrl');
+        $this->validateCallback();
 
         $data = $this->getBaseData();
         $data['METHOD'] = 'SetExpressCheckout';
@@ -34,6 +106,31 @@ public function getData()
         $data['LOCALECODE'] = $this->getLocaleCode();
         $data['CUSTOMERSERVICENUMBER'] = $this->getCustomerServiceNumber();
 
+        $callback = $this->getCallback();
+
+        if (!empty($callback)) {
+            $data['CALLBACK'] = $callback;
+            // callback timeout MUST be included and > 0
+            $timeout = $this->getCallbackTimeout();
+
+            $data['CALLBACKTIMEOUT'] = $timeout > 0 ? $timeout : self::DEFAULT_CALLBACK_TIMEOUT;
+
+            // if you're using a callback you MUST set shipping option(s)
+            $shippingOptions = $this->getShippingOptions();
+
+            if (!empty($shippingOptions)) {
+                foreach ($shippingOptions as $index => $shipping) {
+                    $data['L_SHIPPINGOPTIONNAME' . $index] = $shipping->getName();
+                    $data['L_SHIPPINGOPTIONAMOUNT' . $index] = number_format($shipping->getAmount(), 2);
+                    $data['L_SHIPPINGOPTIONISDEFAULT' . $index] = $shipping->isDefault() ? '1' : '0';
+
+                    if ($shipping->hasLabel()) {
+                        $data['L_SHIPPINGOPTIONLABEL' . $index] = $shipping->getLabel();
+                    }
+                }
+            }
+        }
+
         $data['MAXAMT'] = $this->getMaxAmount();
         $data['PAYMENTREQUEST_0_TAXAMT'] = $this->getTaxAmount();
         $data['PAYMENTREQUEST_0_SHIPPINGAMT'] = $this->getShippingAmount();
diff --git a/src/Support/InstantUpdateApi/ShippingOption.php b/src/Support/InstantUpdateApi/ShippingOption.php
new file mode 100644
index 0000000..aba549d
--- /dev/null
+++ b/src/Support/InstantUpdateApi/ShippingOption.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Omnipay\PayPal\Support\InstantUpdateApi;
+
+class ShippingOption
+{
+    /** @var string */
+    private $name;
+
+    /** @var float */
+    private $amount;
+
+    /** @var bool */
+    private $isDefault;
+
+    /** @var string */
+    private $label;
+
+    /**
+     * @param string $name      L_SHIPPINGOPTIONNAME0
+     * @param float  $amount    L_SHIPPINGOPTIONAMOUNT0
+     * @param bool   $isDefault L_SHIPPINGOPTIONISDEFAULT0
+     * @param string $label     L_SHIPPINGOPTIONLABEL0
+     */
+    public function __construct($name, $amount, $isDefault = false, $label = null)
+    {
+        $this->name      = $name;
+        $this->amount    = $amount;
+        $this->isDefault = $isDefault;
+        $this->label     = $label;
+    }
+
+    /**
+     * @return bool
+     */
+    public function hasLabel()
+    {
+        return !is_null($this->label);
+    }
+
+    /**
+     * @return string
+     */
+    public function getName()
+    {
+        return $this->name;
+    }
+
+    /**
+     * @return float
+     */
+    public function getAmount()
+    {
+        return $this->amount;
+    }
+
+    /**
+     * @return boolean
+     */
+    public function isDefault()
+    {
+        return $this->isDefault;
+    }
+
+    /**
+     * @return string
+     */
+    public function getLabel()
+    {
+        return $this->label;
+    }
+}
diff --git a/tests/Message/ExpressAuthorizeRequestTest.php b/tests/Message/ExpressAuthorizeRequestTest.php
index 16848af..b7186de 100644
--- a/tests/Message/ExpressAuthorizeRequestTest.php
+++ b/tests/Message/ExpressAuthorizeRequestTest.php
@@ -3,6 +3,7 @@
 namespace Omnipay\PayPal\Message;
 
 use Omnipay\Common\CreditCard;
+use Omnipay\PayPal\Support\InstantUpdateApi\ShippingOption;
 use Omnipay\Tests\TestCase;
 
 class ExpressAuthorizeRequestTest extends TestCase
@@ -215,4 +216,158 @@ public function testMaxAmount()
 
         $this->assertSame(321.54, $data['MAXAMT']);
     }
+
+    public function testDataWithCallback()
+    {
+        $baseData = array(
+            'amount' => '10.00',
+            'currency' => 'AUD',
+            'transactionId' => '111',
+            'description' => 'Order Description',
+            'returnUrl' => 'https://www.example.com/return',
+            'cancelUrl' => 'https://www.example.com/cancel',
+            'subject' => 'demo@example.com',
+            'headerImageUrl' => 'https://www.example.com/header.jpg',
+            'allowNote' => 0,
+            'addressOverride' => 0,
+            'brandName' => 'Dunder Mifflin Paper Company, Incy.',
+        );
+
+        $shippingOptions = array(
+            new ShippingOption('First Class', 1.20, true, '1-2 days'),
+            new ShippingOption('Second Class', 0.70, false, '3-5 days'),
+            new ShippingOption('International', 3.50),
+        );
+
+        // with a default callback timeout
+        $this->request->initialize(array_merge($baseData, array(
+            'callback' => 'https://www.example.com/calculate-shipping',
+            'shippingOptions' => $shippingOptions,
+        )));
+
+        $data = $this->request->getData();
+        $this->assertSame('https://www.example.com/calculate-shipping', $data['CALLBACK']);
+        $this->assertSame(ExpressAuthorizeRequest::DEFAULT_CALLBACK_TIMEOUT, $data['CALLBACKTIMEOUT']);
+
+        $this->assertSame('First Class', $data['L_SHIPPINGOPTIONNAME0']);
+        $this->assertSame('1.20', $data['L_SHIPPINGOPTIONAMOUNT0']);
+        $this->assertSame('1', $data['L_SHIPPINGOPTIONISDEFAULT0']);
+        $this->assertSame('1-2 days', $data['L_SHIPPINGOPTIONLABEL0']);
+
+        $this->assertSame('Second Class', $data['L_SHIPPINGOPTIONNAME1']);
+        $this->assertSame('0.70', $data['L_SHIPPINGOPTIONAMOUNT1']);
+        $this->assertSame('0', $data['L_SHIPPINGOPTIONISDEFAULT1']);
+        $this->assertSame('3-5 days', $data['L_SHIPPINGOPTIONLABEL1']);
+
+        $this->assertSame('International', $data['L_SHIPPINGOPTIONNAME2']);
+        $this->assertSame('3.50', $data['L_SHIPPINGOPTIONAMOUNT2']);
+        $this->assertSame('0', $data['L_SHIPPINGOPTIONISDEFAULT2']);
+
+        // with a defined callback timeout
+        $this->request->initialize(array_merge($baseData, array(
+            'callback' => 'https://www.example.com/calculate-shipping',
+            'callbackTimeout' => 10,
+            'shippingOptions' => $shippingOptions,
+        )));
+
+        $data = $this->request->getData();
+        $this->assertSame('https://www.example.com/calculate-shipping', $data['CALLBACK']);
+        $this->assertSame(10, $data['CALLBACKTIMEOUT']);
+    }
+
+    public function testDataWithCallbackAndNoDefaultShippingOption()
+    {
+        $baseData = array(
+            'amount' => '10.00',
+            'currency' => 'AUD',
+            'transactionId' => '111',
+            'description' => 'Order Description',
+            'returnUrl' => 'https://www.example.com/return',
+            'cancelUrl' => 'https://www.example.com/cancel',
+            'subject' => 'demo@example.com',
+            'headerImageUrl' => 'https://www.example.com/header.jpg',
+            'allowNote' => 0,
+            'addressOverride' => 0,
+            'brandName' => 'Dunder Mifflin Paper Company, Incy.',
+        );
+
+        $shippingOptions = array(
+            new ShippingOption('First Class', 1.20, false, '1-2 days'),
+            new ShippingOption('Second Class', 0.70, false, '3-5 days'),
+            new ShippingOption('International', 3.50),
+        );
+
+        // with a default callback timeout
+        $this->request->initialize(array_merge($baseData, array(
+            'callback' => 'https://www.example.com/calculate-shipping',
+            'shippingOptions' => $shippingOptions,
+        )));
+
+        $this->setExpectedException(
+            '\Omnipay\Common\Exception\InvalidRequestException',
+            'One of the supplied shipping options must be set as default'
+        );
+
+        $this->request->getData();
+    }
+
+    public function testNoAmount()
+    {
+        $baseData = array(// nothing here - should cause a certain exception
+        );
+
+        $this->request->initialize($baseData);
+
+        $this->setExpectedException(
+            '\Omnipay\Common\Exception\InvalidRequestException',
+            'The amount parameter is required'
+        );
+
+        $this->request->getData();
+    }
+
+    public function testAmountButNoReturnUrl()
+    {
+        $baseData = array(
+            'amount' => 10.00,
+        );
+
+        $this->request->initialize($baseData);
+
+        $this->setExpectedException(
+            '\Omnipay\Common\Exception\InvalidRequestException',
+            'The returnUrl parameter is required'
+        );
+
+        $this->request->getData();
+    }
+
+    public function testBadCallbackConfiguration()
+    {
+        $baseData = array(
+            'amount' => '10.00',
+            'currency' => 'AUD',
+            'transactionId' => '111',
+            'description' => 'Order Description',
+            'returnUrl' => 'https://www.example.com/return',
+            'cancelUrl' => 'https://www.example.com/cancel',
+            'subject' => 'demo@example.com',
+            'headerImageUrl' => 'https://www.example.com/header.jpg',
+            'allowNote' => 0,
+            'addressOverride' => 0,
+            'brandName' => 'Dunder Mifflin Paper Company, Incy.',
+        );
+
+        $this->request->initialize(array_merge($baseData, array(
+            'callback' => 'https://www.example.com/calculate-shipping',
+        )));
+
+        // from the docblock on this exception -
+        // Thrown when a request is invalid or missing required fields.
+        // callback has been set but no shipping options so expect one of these:
+        $this->setExpectedException('\Omnipay\Common\Exception\InvalidRequestException');
+
+        $this->request->getData();
+    }
+
 }