diff --git a/CRM/Stripe/Check.php b/CRM/Stripe/Check.php
index 3f27e73ad0ce7e5664fc8a26d1f543ef9a9e9c34..057f8eb620ce982cfe769a8d8c609995dfd83505 100644
--- a/CRM/Stripe/Check.php
+++ b/CRM/Stripe/Check.php
@@ -34,6 +34,7 @@ class CRM_Stripe_Check {
     self::checkExtensionFirewall($messages);
     self::checkExtensionSweetalert($messages);
     self::checkIfSeparateMembershipPaymentEnabled($messages);
+    self::checkUpgradeMessages($messages);
   }
 
   /**
@@ -231,4 +232,39 @@ class CRM_Stripe_Check {
     }
   }
 
+  /**
+   * Display messages on version upgrade
+   *
+   * @param array $messages
+   */
+  private static function checkUpgradeMessages(&$messages) {
+    // @todo: When we release 6.7 we need to think about if this should be displayed or not (consider install/upgrade).
+    if ((bool) \Civi::settings()->get('stripe_upgrade66message')) {
+      $message = new CRM_Utils_Check_Message(
+        __FUNCTION__ . 'stripe_upgrade66message',
+        E::ts('Thankyou for upgrading to Stripe 6.6. You MUST check your configuration to make sure it will continue working:
+        <ul>
+          <li><strong>Access AJAX API</strong> permission is required for all users that make payments using Stripe (including the anonymous user).
+          Make sure you update your CMS user roles to include this permission.</li>
+          <li>Billing address fields are now disabled by default (if you require additional fields collect them via a profile).
+          If you require the billing address fields you can enable them in <em>Administer->CiviContribute->Stripe Settings->Disable billing address fields</em>.
+          They will be removed in a future version - if this is a problem please contact <a href="https://mjw.pt/support">MJW</a> and let us know why!</li>
+          <li><a href="https://docs.civicrm.org/mjwshared/en/latest/refunds/">Refund UI</a> is now enabled by default.</li>
+        </ul>'
+        ),
+        E::ts('Stripe: You need to check some settings now that you have upgraded to 6.6'),
+        \Psr\Log\LogLevel::CRITICAL,
+        'fa-money'
+      );
+      $message->addAction(
+        E::ts('I\'ve read this'),
+        E::ts('I\'ve read this and made any necessary configuration changes - don\'t show me this upgrade message any
+      more'),
+        'api3',
+        ['Setting', 'create', ['stripe_upgrade66message' => 0]]
+      );
+      $messages[] = $message;
+    }
+  }
+
 }
diff --git a/LICENSE.txt b/LICENSE.txt
index f3b5be84c8df0a125cf4b484635fab6b51072cbb..89eb271ccae1ca67ffcfa7c390a63856e7481d3c 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -1,5 +1,5 @@
 Package: com.drastikbydesign.stripe
-Copyright (C) 2020, Matthew Wire (MJW Consulting) <mjw@mjwconsult.co.uk>
+Copyright (C) 2021, Matthew Wire (MJW Consulting) <mjw@mjwconsult.co.uk>
 Licensed under the GNU Affero Public License 3.0 (below).
 
 -------------------------------------------------------------------------------
diff --git a/docs/releasenotes.md b/docs/releasenotes.md
index b0133ffab3e53f25d0b77f306694de4d54e9b7a9..89070f5382a2785ca8fad506c592adf0e4ed435b 100644
--- a/docs/releasenotes.md
+++ b/docs/releasenotes.md
@@ -9,10 +9,11 @@ Releases use the following numbering system:
 
 * **[BC]**: Items marked with [BC] indicate a breaking change that will require updates to your code if you are using that code in your extension.
 
-## Release 6.6 (not yet released 2021-03-05)
+## Release 6.6 (not yet released 2021-04-10)
 **Requires mjwshared (Payment Shared) 1.0**
 
-**Requires "Access AJAX API" for anonymous users**
+**Access AJAX API permission is required** for all users that make payments using Stripe (including the anonymous user).
+Make sure you update your CMS user roles to include this permission.
 
 * Support for [Payment Request Button](https://stripe.com/docs/stripe-js/elements/payment-request-button) which provides Google Pay and Apple Pay support.
     * To enable, you must set the "Country" in Stripe Settings and then the payment request button will replace the card element when the client browser supports it.
@@ -25,6 +26,14 @@ Releases use the following numbering system:
 * Use new PaymentProcessorWebhook entity to track/process webhooks and avoid simultaneous processing of events.
 * Fixes to processing `invoice.payment_failed` IPN event (also triggered during 3d secure verification).
 * [!146](https://lab.civicrm.org/extensions/stripe/-/merge_requests/146) Listevent API improvements.
+* Fix [#305](https://lab.civicrm.org/extensions/stripe/-/issues/305),[#293](https://lab.civicrm.org/extensions/stripe/-/issues/293) Allow specifying a static statement descriptor.
+* [!148](https://lab.civicrm.org/extensions/stripe/-/merge_requests/148) Implement testing infrastructure with mock Stripe client and add multiple IPN tests - thankyou [@artfulrobot](https://artfulrobot.uk/).
+* [!147](https://lab.civicrm.org/extensions/stripe/-/merge_requests/147) Multiple improvements to import API - thankyou [Jamie McClelland - ProgressiveTech](https://progressivetech.org/).
+* Retrieve subscriptionID so we don't process charge.failed/invoice.payment_failed simultaneously.
+* Fix showing 'successful' on thankyou page when payment failed because of error 'requires payment method'.
+* Make more javascript strings translatable.
+* Disable billing fields by default.
+* Add 6.6 upgrade message to system checks.
 
 ## Release 6.5.8
 
diff --git a/info.xml b/info.xml
index 52b62dadb6eb981a50e50db5981228b0dfe84f8e..ad533b0e547489eb84ba85478b31976234b0c80f 100644
--- a/info.xml
+++ b/info.xml
@@ -15,11 +15,11 @@
     <author>Matthew Wire (MJW Consulting)</author>
     <email>mjw@mjwconsult.co.uk</email>
   </maintainer>
-  <releaseDate>2021-03-05</releaseDate>
+  <releaseDate>2021-04-10</releaseDate>
   <version>6.6-dev</version>
-  <develStage>alpha</develStage>
+  <develStage>beta</develStage>
   <compatibility>
-    <ver>5.28</ver>
+    <ver>5.35</ver>
   </compatibility>
   <comments>Original Author: Joshua Walker (drastik) - Drastik by Design.
     Jamie Mcclelland (ProgressiveTech) did a lot of the 5.x compatibility work.
diff --git a/settings/stripe.setting.php b/settings/stripe.setting.php
index 41ff491d671f3ccf2d4b992561c7796326426128..b49abb91d2f5352af7c08b56c08da1ccf3ab20cc 100644
--- a/settings/stripe.setting.php
+++ b/settings/stripe.setting.php
@@ -64,10 +64,10 @@ return [
     'name' => 'stripe_nobillingaddress',
     'type' => 'Boolean',
     'html_type' => 'checkbox',
-    'default' => 0,
+    'default' => 1,
     'is_domain' => 1,
     'is_contact' => 0,
-    'title' => E::ts('Disable billing address fields (Experimental)'),
+    'title' => E::ts('Disable billing address fields'),
     'description' => E::ts('Disable the fixed billing address fields block. Historically this was required by CiviCRM but since Stripe 6.x the stripe element collects everything it requires to make payment.'),
     'html_attributes' => [],
     'settings_pages' => [
@@ -192,4 +192,14 @@ If this is empty the "suffix" will be generated by CiviCRM using the information
       ]
     ],
   ],
+  'stripe_upgrade66message' => [
+    'name' => 'stripe_upgrade66message',
+    'type' => 'Boolean',
+    'html_type' => 'checkbox',
+    'default' => 1,
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'title' => E::ts('Show 6.6 upgrade message (system check)'),
+    'html_attributes' => [],
+  ],
 ];