Our tree frog notes: tab usually applies when one (or more) is at a bar/pub and plans to order a series of drinks.

I concur. I also agree that it would be understood in related contexts although probably not primarily used that way. If you're a regular the bartender might ask you if you want to "run a tab" after serving you your first drink. If you indicate that you will be eating before or while ordering the first drink it will probably be assumed that you will get a check for the entire amount when you are done, which may correspond to the finishing of the meal. The bartender would ask you if you'd like anything else after clearing the dishes. This is all assuming that you are eating at the bar, which is not common if you are in a group but not that rare if you are alone.