What happens to a tag if an account name changes?

If an account name has changed in your accounting system, and this account has been tagged in RealTime CEO, the existing account will remain on the Monthly Data screen with all of its history.  However, the new account name will not be tagged when you load the next month of data and should be tagged.  The result will be two accounts on the Monthly Data screen, one with history up to the previous month, and the new one with no history but a value in the current month. These two accounts can be merged.  See How to Merge accounts