@ssu11321 If the medical miles box is prefilled with a 0 and you are using the TurboTax desktop edition for Windows, there are probably Supporting Details for that box that needs to be removed.
Put your cursor in the mileage box. Then click on Edit at the top of the desktop program screen. Click on Add Supporting Details then click on Remove at the top of that window. You should now be able to enter the mileage.
