Hello there, @SCS63.
Please know that QuickBooks Self-Employed (QBSE) doesn't currently have a feature that automatically maps mortgage interest expenses to Box 44.
To ensure accurate reporting on your self-assessment, you can categorize the interest portion of your mortgage payment under a general category such as Other Business Expense or Rent or Lease Payments. For clarity, you can add a message specifying "Mortgage Interest – Residential Property (Box 44)."
If you need guidance on selecting the best category or assistance with the process, consider contacting your accountant.
You can reply to this thread if you have additional questions. We're here to help.