If your state has no income tax, there should be no state tax withheld in box 17 of the 1099-INT. In that case, you do not need anything in box 15. Leave boxes 15, 16, and 17 empty. Do not enter anything. Do not enter zero in box 17. Just leave it empty.
To avoid this altogether, on the screen that asks if any uncommon situations apply, do not check the box for "State income taxes were withheld" if box 17 on the 1099-INT is blank or zero.
