Geoffrey E. answered  03/14/19
From Getting Medieval to Moving through the Digital Age
While the UK and Commonwealth countries can point to a singular example--the Monarch--for "official" English, there's not necessarily a formal body making such determinations in them.
In the US, there's not even the centerpiece of a monarch to follow. The closest that we come are the several style guides--notably MLA, APA, Chicago, and AP--which make sometimes-conflicting assertions regarding preferred usage. Always check which is to be used.