The Accounting API has previously used version numbers on classes to indicate when changes have been made, for example CODAAPIBudget_8_0 would be slightly different from CODAAPIBudget_7_0 in either declared functions or the semantics of those functions.
New classes are no longer following this practice but you will find many existing classes in the API that do. For classes that contain version numbers current practice is to release a new version of the class if a non-backwards compatible change has been made. For example, adding a new function would not result in a new version but changing the behaviour of an existing function would.
If you are making use of a WSDL file to access the API as a Web Service we recommend you update the WSDL file for each new major version to ensure you can access all functions correctly.