I don't think you read the question correctly.  That's OK.  I am not looking at the deduction on Schedule A.  I am looking at the interest income on Schedule B because my client is the seller.

Here is the full diagnostic -

Interest Income Item #2: Enter a valid social security number for all seller-financed mortgage interest income sources. The IRS does not allow EINs for seller-financed mortgage interest. The SSN must be in the valid range for SSNs. It must contain nine digits and cannot be all zeros or nines.