The current version of the Payments API is
Any incompatible changes to the API will result in incremented versions of the API, which will change the resource URLs.
At some point, the current version will be announced as
Deprecated and you will have 12 months to switch your applications to a newer version of the API.
All clients will be notified of any deprecation in the API.
New fields can be added to the current API version, at any time without preliminary warning with subsequent documentation added afterward. However, already documented fields cannot be modified or removed. Please rely solely on them.