No, don't combine the 1098 Mortgage Interest Forms. Enter all the information from the first 1099-Mortgage Interest Form (original loan). Mark that it was sold when TurboTax asks. Next, enter the second 1099-Mortgage Interest Form. Don't enter that the second one was refinanced since the mortgage wasn't refinanced, just sold.
The outstanding mortgage principal will be in box 2 of the current servicer. There shouldn't be an outstanding mortgage principal for the original servicer since the loan was transferred.
Refer to the TurboTax article How do I handle multiple 1098 mortgage forms in TurboTax Online? for additional information.
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