Where exactly does TurboTax ask for a unit number? In the mailing address in the My Info section there is a space for Apt. #, but you can leave it blank. I'm not aware of any place in the federal section where it would ask for a unit number, or any reason that it would matter whether you live in a house or an apartment. Is that question coming up in the state section? If so, what state is it, and what topic in the state section is it in?