Updated October 18, 2026. Quick answer: The Table 1 worksheet in Publication 936 works out your qualified loan limit and then how much of your home mortgage interest is deductible when your mortgage balances run above that limit. Part I finds the limit on line 11, and Part II turns it into the deductible amount on line 15, which goes on Schedule A.
Related reading on this site: IRS Publication 530.
More IRS forms and schedules for individual filers, read line by line: Form 8396 instructions.
Related reading on this site: IRS Publication 936.
What this worksheet is for
Publication 936 says when you can skip the worksheet: “You can deduct all of the interest you paid during the year on mortgages secured by your main home or second home in either of the following two situations.” “All the mortgages are grandfathered debt.” “The total of the mortgage balances for the entire year is within the limits discussed earlier under Home Acquisition Debt.” “In either of those cases, you don’t need Table 1.” “Otherwise, you can use Table 1 to determine your qualified loan limit and deductible home mortgage interest.”
There is one worksheet per return: “Fill out only one Table 1 for both your main and second home regardless of how many mortgages you have.” The Form 1098 boxes are covered at Form 1098 box 1, Form 1098 box 2 and boxes 3 and 11 (origination and acquisition dates).
The worksheet line by line
The title of the worksheet is “Worksheet To Figure Your Qualified Loan Limit and Deductible Home Mortgage Interest for the Current Year”, and it points back with “See the Table 1 Instructions.”
| Line | What the worksheet says |
|---|---|
| Part I, 1 | “Enter the average balance of all your grandfathered debt.” |
| Part I, 2 | “Enter the average balance of all your home acquisition debt incurred after October 13, 1987, and prior to December 16, 2017.” |
| Part I, 3 | “Enter $1,000,000 ($500,000 if married filing separately)” |
| Part I, 4 | “Enter the larger of the amount on line 1 or the amount on line 3.” |
| Part I, 5 | “Add the amounts on lines 1 and 2. Enter the total here” |
| Part I, 6 | “Enter the smaller of the amount on line 4 or the amount on line 5.” “If you have no home acquisition debt incurred after December 15, 2017, or the amount on line 6 is $750,000 ($375,000 if married filing separately) or more, line 6 is your qualified loan limit.” |
| Part I, 7 | “Enter the average balance of all your home acquisition debt incurred after December 15, 2017.” |
| Part I, 8 | “Enter $750,000 ($375,000 if married filing separately)” |
| Part I, 9 | “Enter the larger of the amount on line 6 or the amount on line 8.” |
| Part I, 10 | “Add the amounts on lines 6 and 7. Enter the total here” |
| Part I, 11 | “Enter the smaller of line 9 or line 10. This is your qualified loan limit” |
| Part II, 12 | “Enter the total of the average balances of all mortgages from lines 1, 2, and 7 on all qualified homes.” |
| Part II, 13 | “Enter the total amount of interest that you paid on the loans from line 12.” |
| Part II, 14 | “Divide the amount on line 11 by the amount on line 12. Enter the result as a decimal amount (rounded to three places)” |
| Part II, 15 | “Multiply the amount on line 13 by the decimal amount on line 14. Enter the result. This is your deductible home mortgage interest.” |
| Part II, 16 | “Subtract the amount on line 15 from the amount on line 13. Enter the result. This isn’t home mortgage interest.” |
The worksheet’s own bullet under line 12 tells you when to stop: “If line 11 is equal to or more than line 12, stop here.” It also says “All of your interest on all the mortgages included on line 12 is deductible as home mortgage interest on Schedule A (Form 1040).”
A worked example
Illustration, not an IRS example. Every balance and the interest paid are invented. The $1,000,000 on line 3 and the $750,000 on line 8 are the amounts printed on the worksheet for filers who are not married filing separately. Line 14 is divided and rounded to three places, so 750,000 divided by 900,000 = 0.83333 becomes 0.833.
| Item | Illustration |
|---|---|
| Line 1 (invented average balance for line 1) | $0 |
| Line 2 (invented average balance for line 2) | $600,000 |
| Line 3 (printed on the worksheet) | $1,000,000 |
| Line 4, larger of line 1 or line 3 | $1,000,000 (computed) |
| Line 5, add lines 1 and 2 | $600,000 (computed) |
| Line 6, smaller of line 4 or line 5 | $600,000 (computed) |
| Line 7 (invented average balance for line 7) | $300,000 |
| Line 8 (printed on the worksheet) | $750,000 |
| Line 9, larger of line 6 or line 8 | $750,000 (computed) |
| Line 10, add lines 6 and 7 | $900,000 (computed) |
| Line 11, smaller of line 9 or line 10 | $750,000 (computed) |
| Line 12, add the balances from lines 1, 2 and 7 | $900,000 (computed) |
| Line 13 (invented interest paid) | $30,000 |
| Line 14, line 11 divided by line 12, rounded to three places | 0.833 (computed) |
| Line 15, line 13 x line 14 | $24,990 (computed) |
| Line 16, line 13 minus line 15 | $5,010 (computed) |
In this illustration line 11 is less than line 12, so the worksheet continues to line 13. Line 15 is the deductible part and line 16 is the part that is not home mortgage interest. Because line 14 is rounded before it is used, the result differs from an unrounded calculation: 30,000 x (750,000 / 900,000) = 25,000, which is 10 more than line 15 here. The worksheet tells you to use the rounded decimal.
Where the number comes from
Lines 1, 2, 7 and 12 are average balances. The publication explains: “You have to figure the average balance of each mortgage to determine your qualified loan limit.” “You need these amounts to complete lines 1, 2, 7, and 12 of Table 1.” “You can use the highest mortgage balances during the year, but you may benefit most by using the average balances.”
The publication gives separate worksheets for those averages, which are not reproduced here. They are named “Average of first and last balance method.” “Interest paid divided by interest rate method.” and “Statements provided by your lender.” A loan that fits more than one group has its own rules under the heading for mixed-use mortgages. Read those in your own copy of Publication 936. Line 13 is simply “the total amount of interest that you paid on the loans from line 12.”
Where it goes next
Line 15 ends: “This is your deductible home mortgage interest. Enter this amount on Schedule A (Form 1040)”. See Schedule A (Form 1040) and Schedule A line 8a for the Form 1098 interest line. The Schedule A result is then carried to Form 1040 on the line captioned “Standard deduction or itemized deductions (from Schedule A)”.
Edition and line numbers
This page reads the 2025 edition of Publication 936, the edition for the tax year 2025 return filed in 2026. The Table 1 worksheet in it has Part I (lines 1 to 11) and Part II (lines 12 to 16). Check the tax year printed on the worksheet in your own copy and use that year’s line numbers, because a different year’s worksheet can number or word its lines differently.
Common mistakes
- Filling out one worksheet per home. The publication says “Fill out only one Table 1 for both your main and second home regardless of how many mortgages you have.”
- Skipping the average balances and using a single year-end figure. The publication says you need average balances for lines 1, 2, 7 and 12: “You need these amounts to complete lines 1, 2, 7, and 12 of Table 1.”
- Forgetting that line 14 is rounded. The worksheet says “(rounded to three places)”.
Related: Form 1098 box 1, Form 1098 box 2, origination and acquisition dates, Schedule A (Form 1040), and Schedule A line 8a.
Sources
- Publication 936, Home Mortgage Interest Deduction (2025 returns): https://www.irs.gov/pub/irs-pdf/p936.pdf
- Form 1040 (2025): https://www.irs.gov/pub/irs-pdf/f1040.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.