When we make backwards-incompatible changes to the WePay API, we release a new dated version. Your app continues to be on the current version of the API to avoid breaking your code. You can follow our Versioning Tutorial to upgrade to the latest API version.
Your app’s WePay API Version determines the behavior that you see from the API. It affects the parameters you can pass in, the response that you get back, and the IPNs you receive.
WePay API versions are dates with format yyyy-mm-dd. Ex: 2011-01-15.
The current version of the WePay API is 2016-07-1. Full list of API versions can be found here - List of WePay API Versions.
You can check your application’s API version on the configure tab of your application dashboard:</p>
If you are not on the latest version of the WePay API, follow the link for more information on how to upgrade your application’s API Version:
How to Upgrade Version Tutorial.
Following changes are considered to be backwards incompatible changes to the WePay API</p>