Line 8b
If you paid home mortgage interest to a recipient who didn’t provide you a Form 1098, report your deductible mortgage interest on line 8b. Your deductible mortgage interest may be less than what you paid if one or more of the limits on home mortgage interest apply to you. For more information about these limits, see Limits on home mortgage interest , earlier.
Seller financed mortgage.
If you paid home mortgage interest to the person from whom you bought the home and that person didn’t provide you a Form 1098, write that person's name, identifying number, and address on the dotted lines next to line 8b. If the recipient of your home mortgage payment(s) is an individual, the identifying number is their social security number (SSN). Otherwise, it is the employer identification number (EIN). You must also let the recipient know your SSN.
If you don't show the required information about the recipient or let the recipient know your SSN, you may have to pay a $50 penalty.
Interest reported on someone else’s Form 1098.
If you and at least one other person (other than your spouse if filing jointly) were liable for and paid interest on the mortgage, and the home mortgage interest paid was reported on the other person’s Form 1098, identify the name and address of the person or persons who received a Form 1098 reporting the interest you paid. If you are filing a paper return, identify the person by attaching a statement to your paper return and printing “See attached” to the right of line 8b.