by Jim » Fri Apr 24, 2015 3:57 pm
What type of modifications are you wanting to make?
There is no API for the Payment/Checkout screen. You can make modifications to the screen using the custom template interface by adding css, javascript etc. in the shopping cart template that is assigned on Commerce Setup > Order System > Layout Info screen. The templates can be edited on the Merchandising > Custom Templates > screen. You can add custom javascript to the checkout screen by putting it in the field "Javascript added at start of built-in CheckIt function:" on the Commerce Setup > Order System > Checkout screen (In Pro stores only)