The checkout isn't really built to allow you to move/copy the promotion code functionality there from the cart view. While it's possible to do this still, it would be a lot of work in the viewset and would also require that you create a custom Web API endpoint for the checkout to talk to in order to duplicate the functionality found in the cart.

In regards to the postback, I've created an issue for this to be discussed and possibly implemented at some point.

https://github.com/Hotcak...merce/core/issues/70

Thanks Will! For now I've managed to override the behaviour using ajax requests. While it's not the best approach, it's an imminent client requirement for me. I'll try and make some time to write proper endpoints for this and make it a bit more SPA friendly. Once done I'll send a pull request.

Thanks for the update. :)

On a side note... Please remember to create an issue for anything you wish to submit a pull request for (if it doesn't already exist).