Be sure to enter 0 (zero) as the ending (01/01/2019) balance of the loan that was bought. 

make sure Box 2 has the beginning balance of the loan for either 

January 1, of the tax year (in this case 01/01/2018)

OR

The balance on the date the loan was originated or transferred if originated or transferred in the tax year  (in this case 2018)

[edited 02/11/2019 I 5:34 PM]

Any idea about the Ending Mortgage Balance? On the mortgage for the mortgage that purchased the original mortgage?

Still receiving an error because Box 2 from the bank that purchased the mortgage mid year 2018 shows a zero which the TurboTax program can not calculate correctly?

Please change that number to be the outstanding principal on the loan when it was transferred.

 The IRS has changed the wording for Box 2 for just this situation. Instructions were- "Box 2. Shows the outstanding mortgage principal on the mortgage as of January 1, 2018."
But they are changing it to- "Box 2. Shows the outstanding principal on the mortgage as of January 1,  If the mortgage originated in 2018, shows the mortgage principal as of the date of origination. If the recipient/lender acquired the loan in 2018, shows the mortgage principal as of the date of acquisition."

That

That finally worked for me. In summary for others with a mortgage that was purchased by another bank in 2018...when entering the mortgage from the former bank enter the information for Boxes 1-3 the same way then on the next page when asked for “Ending mortgage balance” enter the balance that was transferred to the new, purchasing bank.

For the purchasing bank/current bank that now has your mortgage, Boxes 1&3 and the taxes enter those figures as seen on the mortgage statement. Box 2- Do NOT enter zero, rather enter the same figure that was transferred from the previous bank.

In the Ending Mortgage balance- enter the last principal balance of your mortgage of 2018. For my mortgage the last payment was December 1, 2018 so that was my Ending balance of the year as my next payment was the following year.

Enter property taxes and insurance premiums as they appear on your statements for each bank. Hope that helps

Thank you.