If the mortgage company didn't credit a portion of the payoff until January 2018, that may be the reason you received the 1098. It might be worth checking with them to get clarification. If you itemize your deductions on your 2018 return, you would be entitled to claim the mortgage interest and taxes if it has been reported correctly.
[Edited 02.09.2019 | 4:36 pm PST]
