How would you pronounce the following when answering a phone for a boss whose last name is Beltz? Some people are saying Mr. Beltz’s office, pronouncing the extra s, and someone else thinks you should just say Mr. Beltz office.
Which one is it?
It’s certainly Mr Beltz’s office. Otherwise it sounds like it belongs to one Mr Belt. See this answer to Which singular names ending in “s” form possessives with only a bare apostrophe? for details.