Deductions & credits

For the outstanding balance, enter the amount you owed on the RV on 01/01/2021, so the balance at the beginning of the year, not the end of the year. There is a box you can mark if you did not get a 1098.   Go back and edit your answers and mark that box.  You will be asked for the lender's address and their SSN/EIN as well as the amount of interest, outstanding balance on 01/01/2021 and the date you took out the loan.      

You're allowed to deduct the interest on a loan secured by your main home (where you ordinarily live most of the time) and a second home.

A mobile home, RV, house trailer, or houseboat that has sleeping, cooking, and toilet facilities counts as a main or second home, and as long as it meets all the other requirements for deducting mortgage interest, you can claim the interest like an immovable home.