Error with the program? While entering mortgage interest for home expenses, I list two mortgages with interest, but only the first loan interest is carried forward.

Review your entries in the mortgage interest section. If you entered the loans in a way that indicates both loans were carried at the same time, and the amount of debt with the second loan exceeded $750,000 in total, this could be the reason you aren't seeing the interest from the second loan.

If, for example, you had two lenders because the loan was sold during the year, enter the two Forms 1098 following these steps:

Enter the original (sold) loan first:

1. Sign in to TurboTax and select Pick up where you left off or Review/Edit under Deductions & Credits.
2. Select Show more next to Your Home and Start or Revisit next to Mortgage Interest and Refinancing (Form 1098).
3. Answer Did you pay any home loans in 2023? and Continue.
4. You can either sign in to your financial institution and import your 1098 forms, or select Change how I enter my form.
5. Next, you can either upload a digital copy or Type it in myself.
6. Continue through and be sure to enter this 1098 exactly as it appears.
7. Answer the questions, and when you get to the Let's see if this is the most recent form for this loan screen, answer No to Is the 1098 you're working on now the most recent for your loan?.
8. On the next Let's get some details about this loan screen, answer Yes to Is this the original loan you used to buy your property?
9. Select Continue to be taken back to the Your 1098 info so far screen.

Then enter the 1098 for the new loan

1. On the Your 1098 info so far screen, select Add another 1098 and continue through to either import or enter your information manually.
2. Answer the questions accordingly and complete your 1098 info exactly as it appears on your form.
3. On the Let's see if this is the most recent form for this loan screen, answer Yes to Is the 1098 you're working on now the most recent for your loan?
4. On the next Let's get some details about this loan screen, answer Yes to Is this the original loan you used to buy your property? Even though the loan is with a new lender, it's still considered the original loan for this calculation.
5. When you're all done, you'll see both your forms on the Your 1098 info so far screen. You can Continue through to finish and file your return.

See this TurboTax help article for more information.