If the loan was transferred to another bank or lender mid-year, then you should have two 1098's. The one from the old lender should show the 1/1/2018 balance, while the one from the new lender will show the 12/31/2018 balance. The 1/1/2018 balance is absolutely required.
Hopefully you can log on to your mortgage account online to see the payment and balance history and see what the balance was "before" you made that 1/1/2018 payment. All of your payment history "should" have carried over to the new lender since they just assumed an existing loan and you didn't refinance or anything like that.
