Shared interest reported on someone else's Form 1098.

If the shared interest was reported on the other person's Form 1098, report your share of the interest on line 8b (as explained in Line 8b , later).

Form 1098 doesn’t show all interest paid.

If you paid more interest to the recipient than is shown on Form 1098, include the larger deductible amount on line 8a and explain the difference. If you are filing a paper return, explain the difference by attaching a statement to your paper return and printing “See attached” to the right of line 8a.

If you are claiming the mortgage interest credit (for holders of qualified mortgage credit certificates issued by state or local governmental units or agencies), subtract the amount shown on Form 8396, line 3, from the total deductible interest you paid on your home mortgage. Enter the result on line 8a.