This requires you to know up front which expenses you want to track, though. If you don't, and you change your mind later, you get to do that table scan anyway,

This requires you to know up front which expenses you want to track, though. If you don't, and you change your mind later, you get to do that table scan anyway, so you may as well actually record the metadata that makes it possible. edit: I read what you're describing here as a single entry system if you just read "expense account" as "expense type"; double entry would be if you physically recorded each of those in two places. It's entirely possible we're arguing about semantics.