You may use the request header X-API-Version to specify your expected API version. The currently supported versions are:
If the version header is omitted, then by default the most recent version of the API will be used to process your request. If this default version is not backwards-compatible with the (presumably older) version that you expect, then the request processing and response may be unexpected or erroneous.
If the version header is supplied and matches a supported version, then that version will be used to process the request.
If the version header is supplied and does not match a supported version, then the response will have status 501.
% curl -H "X-API-Version: 0.8.0" https://app.liquidplanner.com/api/account
"message": "The version you requested is not implemented.",