Outstanding Mortgage Principal as of 12/31/2018, but my 1098 Box 2 says Outstanding Mortgage Principal as of 1/1/2018. So, how do I know what to enter in TurboTax?

[Gaypana]

TurboTax asks for as of 12/31/2018. But my 1098 says as of 1/1/2018. So, How do I get the number for 12/31/2018? The accountant letter tells me "mortgage amortization". Do I use that?

[KrisD]

Yes, that should have the ending principal (loan) balance reported. 

It should be the principal after the December payment as long as you are not making additional payments on the principal. 

Box 2 should report the 01/01/2018 balance, but you will need to look at a statement (or call your lender) to get the 12/31/2018 balance.