If you are completing immigration forms, you should be aware of the recent policy and practice changes by USCIS, which is now rejecting applications unless every box in the immigration form is completed, at least with NA, even if obviously irrelevant to your client’s application. The Washington Post story below explains these changes and the consequences for not filling in blanks, even where the absence of an answer was obvious (e.g., an applicant with no middle name or no apartment number).
I think this has been best practice, though in my experience putting “NA" in the first box of an irrelevant section had been enough, and I can’t recall whether I ever put "NA" in the apartment number box when the client didn’t live in an apartment….