Updated October 18, 2026. Quick answer: Line 8a is for home mortgage interest and points that your lender reported to you on Form 1098. You enter the deductible amount, which is the Form 1098 figure unless one of the limits on home mortgage interest applies to you. The instructions also cover shared loans and a Form 1098 that understates what you paid.
More IRS forms and schedules for individual filers, read line by line: Form 8396 instructions.
Related reading on this site: IRS Publication 936.
IRS worksheets read line by line: Home Mortgage Interest Limit Worksheet.
What line 8a asks for
The form’s caption reads “Home mortgage interest and points reported to you on Form 1098. See instructions if limited”. The instructions say “Enter on line 8a mortgage interest and points reported to you on Form 1098 unless one or more of the limits on home mortgage interest apply to you.” The statement itself is explained on the Form 1098 page, and the interest box is covered on the Form 1098 box 1 page.
The instructions define the loan this way: “A home mortgage is any loan that is secured by your main home or second home, regardless of how the loan is labeled.” They add “It includes first and second mortgages, home equity loans, and refinanced mortgages.”
Where the number comes from
Start with the interest and points on the Form 1098 you received. Then check whether a limit applies. The instructions say “deduction for home mortgage interest is subject to a number of limits. If one or more of the following limits applies, see Pub. 936 to figure your deduction.” If your deduction is limited, the line 8a instruction is “Only enter on line 8a the deductible mortgage interest and points that were reported to you on Form 1098.”
The first limit concerns what the loan paid for: “Make sure to check the box on line 8 if you had one or more home mortgages in 2025 with an outstanding balance and you didn’t use all of the loan proceeds to buy, build, or substantially improve the home.” The box is on line 8 of the form, whose caption reads “If you didn’t use all of your home mortgage loan(s) to buy, build, or improve your home, see instructions and check this box”.
The instructions set out further limits under these headings: “Limit on loans taken out on or before December 15, 2017.” “Limit on loans taken out after December 15, 2017.” and “Limit when loans exceed the fair market value of the home.” The dollar amounts and any exceptions are in the instructions and in Pub. 936, so read those before entering a limited figure.
Special cases on line 8a
If more than one person is on the loan: “If you and at least one other person (other than your spouse if you file a joint return) were liable for and paid interest on a mortgage that was your home, you can only deduct your share of the interest.” When the Form 1098 is in your name, “deduct only your share of the interest on line 8a.” When it is in someone else’s name, “report your share of the interest on line 8b”. That case is covered on the Schedule A lines 8b, 8c and 8e page.
If the form shows too little: “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 the form shows a refund: “If your Form 1098 shows any refund of overpaid interest, don’t reduce your deduction by the refund.” The instructions send you to the instructions for Schedule 1 (Form 1040), line 8z, for that refund.
If you hold a mortgage credit certificate: “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.”
Where it goes next
Line 8a is the first of the amounts added on line 8e. The form describes line 8e as “Add lines 8a through 8c”. Line 8e then flows into line 10, which reads “Add lines 8e and 9”. See Schedule A lines 8b, 8c and 8e for line 8e and Schedule A lines 9 and 10 for line 10. Line 10 is part of the total on line 17, covered on the Schedule A lines 17 and 18 page. The overall form is explained on the Schedule A (Form 1040) page.
Edition and line numbers
This page reads the 2025 Schedule A (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040 or 1040-SR.” Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Entering the Form 1098 amount without checking for a limit. The instructions say to enter the amount “unless one or more of the limits on home mortgage interest apply to you.”
- Deducting the whole amount when the loan was shared. The instructions say “you can only deduct your share of the interest.”
- Reducing the deduction by a refund of overpaid interest. The instructions say “don’t reduce your deduction by the refund.”
Related: Schedule A (Form 1040), Form 1098, and Form 1098 box 1.
Sources
- Instructions for Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/i1040sca.pdf
- Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/f1040sa.pdf
Read from the IRS documents linked above on October 18, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.