Quick reality check you will appreciate, Form 14900 is an IRS worksheet that is usually sent during a correspondence exam. You complete it to prove the correct mortgage interest deduction for the year, using average mortgage balances and the long standing caps, 1,000,000 for older grandfathered or pre‑December 16, 2017 acquisition debt and 750,000 for post‑December 15, 2017 acquisition debt, with lower amounts for married filing separately.
Only submit Form 14900 if the IRS asked you to. If you received the letter, you can complete the worksheet online in the IRS wizard or download the PDF to submit by fax or mail.
Key takeaways
- Form 14900 is an IRS worksheet used to prove your home mortgage interest deduction, most often during correspondence exams, and it follows the same framework as Publication 936’s Table 1 worksheet.
- The worksheet caps remain, 1,000,000 for grandfathered or pre‑12/16/2017 acquisition debt and 750,000 for acquisition debt incurred after 12/15/2017, with 500,000 and 375,000 caps for married filing separately, respectively.
- You calculate the average mortgage balance by adding the monthly closing or average balances and dividing by the number of months the mortgage was a qualified home loan, usually 12. Month end precision matters.
- Pull support from lender statements and Form 1098, keep a copy of the calculation and any reconciliations, and label mixed‑use debt clearly.
- If the IRS did not request Form 14900, you typically use Publication 936’s worksheet to compute the same limitation for your Schedule A.
What Form 14900 is, and when you actually need it
Form 14900, “Worksheet for Qualified Loan Limit and Deductible Home Mortgage Interest for Tax Years Beginning after 2017,” walks you through lines 1 to 16 to determine two things, your qualified loan limit and the portion of interest you can deduct on Schedule A. The IRS mails this worksheet with exam letters, for example Letter 566 series, to help you compute the correct amount and show your work. You can complete it in the IRS online wizard or download a PDF for submission.
If you are filing without an IRS request, the same math lives in Publication 936’s “Table 1, Worksheet To Figure Your Qualified Loan Limit and Deductible Home Mortgage Interest,” and you keep that calculation with your records. In other words, Form 14900 is the IRS’s way of asking you to document the Pub 936 computation during an exam.
A quick plain‑English map of the rules
- “Grandfathered debt” is the average balance of mortgages secured by qualified homes on October 13, 1987, which remains fully deductible within the older cap framework.
- “Home acquisition debt” covers loans used to buy, build, or substantially improve a qualified home, with the older 1,000,000 cap for debt taken out after 10/13/1987 and before 12/16/2017, and 750,000 for debt incurred after 12/15/2017. Special written binding contract relief exists for late‑2017 purchases closed by April 1, 2018.
- Mixed‑use mortgages require splitting balances by category, for example part acquisition, part home equity. You compute separate average balances for each category before you finish the worksheet.
How the average mortgage balance works
Here is the piece that causes most headaches. You figure an average for each mortgage by adding either the monthly closing balance or the lender’s monthly average balance, then dividing by the number of months the home was a qualified home for that mortgage. The IRS specifically allows you to use monthly closing balances or monthly average balances from statements, and if your lender can provide a single annual average, you can use that. Stay strict, use the month end balances, not partial‑month estimates.
Why this matters, the average balance feeds four Form 14900 lines, lines 1 and 2 for older categories, line 7 for post‑2017 acquisition debt, and line 12 for the total average of all mortgages. Those four numbers drive the cap comparison and the final deductible interest you enter on Schedule A.
Documentation you should gather first
- Form 1098 for each lender, plus the interest totals and year‑to‑date principal.
- Monthly statements or an amortization schedule that shows each month end principal balance.
- Notes showing how proceeds were used, buy, build, or improve, refinance details, and any cash‑out uses.
If you run a firm and your team handles dozens of these each season, put the documents in a single workpaper folder, name files consistently, and keep a calculator tab that mirrors Form 14900 lines. That structure shortens reviews and prevents rework.
Step by step, completing Form 14900 in 2025
You will see two groups of lines, Part I determines the qualified loan limit, Part II applies it to your interest.
- Lines 1 and 2, average balances for older buckets
- Line 1, add the average balances of all mortgages you had on qualified homes on October 13, 1987, this is the “grandfathered debt” bucket.
- Line 2, add the average balances of home acquisition debt taken out after 10/13/1987 and before 12/16/2017. Apply the special 2017 purchase relief only if the binding contract and closing dates fit the rules.
- Lines 3 through 6, compare to the 1,000,000 cap
- Line 3, enter 1,000,000 or 500,000 if married filing separately.
- Line 4, take the larger of line 1 or line 3.
- Line 5, add lines 1 and 2.
- Line 6, take the smaller of lines 4 or 5. This is your cap result for older buckets.
- Lines 7 through 11, include post‑2017 acquisition debt and compare to 750,000
- Line 7, add the average balances of all acquisition debt incurred after 12/15/2017.
- Line 8, enter 750,000 or 375,000 if married filing separately.
- Line 9, larger of line 6 or line 8.
- Line 10, add lines 6 and 7.
- Line 11, smaller of line 9 or line 10, this is your qualified loan limit.
- Lines 12 through 16, calculate deductible interest
- Line 12, total average balances of all mortgages from lines 1, 2, and 7.
- Line 13, the total interest you paid on those loans, usually from Forms 1098 plus any additional eligible interest. Do not include points on this line.
- Line 14, divide line 11 by line 12, round to three decimals.
- Line 15, multiply line 13 by the decimal on line 14, that result is your deductible home mortgage interest for Schedule A.
- Line 16, the rest of line 13 is not home mortgage interest for Schedule A purposes.
How to compute the average balance the IRS way
Publication 936 allows two practical approaches, both are acceptable if the mortgage was secured by a qualified home all year and you paid interest monthly. Use either the monthly closing balance or the monthly average balance from the statement. Add those 12 numbers and divide by 12. If your loan started midyear, divide by the number of months you had a month end balance. If your lender provides a single annual average, you can use it.
Small example of the average balance method
Imagine a new mortgage opened on March 1. You have month end balances for March through December:
| Month | Balance |
| Mar | 480,000 |
| Apr | 478,900 |
| May | 477,750 |
| Jun | 476,600 |
| Jul | 475,450 |
| Aug | 474,300 |
| Sep | 473,150 |
| Oct | 472,000 |
| Nov | 470,850 |
| Dec | 469,700 |
Add the ten month end balances, then divide by 10. That result is your average balance for line 7. Keep the statement PDFs as support in your workpapers.
Mixed‑use mortgages, split before you add
If a single loan funded multiple uses, for example part of a cash‑out refinance went to renovations and part went to personal expenses, you have to split the balances by category and compute separate average balances. Publication 936 includes examples showing how monthly payments reduce one category before the other and how that affects the average. You will include the acquisition portion in line 1, 2, or 7 as appropriate, not the personal portion.
What to attach or keep
- The completed Form 14900, the IRS request letter, and any schedules or notes that explain your categories.
- Form 1098 for each lender, plus monthly statements or an amortization report.
- A short memo that ties each loan to its use, for example “2019 purchase,” “2023 remodel,” or “2024 cash‑out used for investments.” This memo saves time in reviews and in any follow‑up questions.
Tip from the review chair, label files with the tax year first, then lender, then last four of the loan number, for example “2025_LenderA_1234_Monthlies.pdf.” Clean names speed up reviewer checks and reduce back‑and‑forth.
A worked example you can follow
Say you have two loans in 2025. Loan A is an older acquisition mortgage from 2016, average balance $620,000. Loan B was opened in 2022 for a kitchen addition, average balance $180,000. You file jointly.
- Line 1, grandfathered debt, none, enter 0.
- Line 2, pre‑12/16/2017 acquisition debt, $620,000.
- Line 3, cap is $1,000,000.
- Line 4, larger of line 1 or line 3, $1,000,000.
- Line 5, add lines 1 and 2, $620,000.
- Line 6, smaller of line 4 or line 5, $620,000.
- Line 7, post‑12/15/2017 acquisition debt, $180,000.
- Line 8, cap is $750,000.
- Line 9, larger of line 6 or line 8, $750,000.
- Line 10, add lines 6 and 7, $800,000.
- Line 11, smaller of line 9 or line 10, your qualified loan limit, $750,000.
Now Part II, assume total average balances of all mortgages, line 12, $800,000, and total interest paid, line 13, $31,000.
- Line 14, $750,000 ÷ $800,000 = 0.938.
- Line 15, deductible home mortgage interest, $31,000 × 0.938 = $29,078.
- Line 16, interest not deductible as home mortgage interest, $1,922. Keep in mind, some of that could be deductible elsewhere if it ties to business or investment uses and you meet those specific rules.
Frequent mistakes that trigger questions
- Using partial month balances instead of month end numbers, or mixing closing and average balances in the same calculation. The IRS allows either monthly closing or monthly average, just be consistent.
- Treating a HELOC as fully deductible when part of the proceeds were used for non‑improvement personal expenses. Only the buy, build, or improve portion counts as acquisition debt for Schedule A.
- Forgetting the married filing separately caps, $500,000 for the older bucket and $375,000 for post‑2017 acquisition debt.
- Putting points on Form 14900’s interest line 13. Points have special rules, see Pub 936’s “Points” section and your Schedule A instructions.
Review checklist before you submit or file
- Do your loan categories reconcile to actual uses of proceeds.
- Do your monthly balances foot to the lender statements.
- Do your line 11, 12, 13 math and rounding match the worksheet instructions.
- Do you have a one‑page cover note that explains any refinances, mixed‑use allocations, or contract‑date exceptions.
For firm owners and review partners
If your firm processes dozens of these worksheets at peak, the problem is rarely a lack of clients, it is delivery sprawl. Standardize your 14900 workpaper and enforce a two step review, preparer then senior, with a final reviewer spot check. That structure cuts revision cycles, shortens partner review time, and protects margins in busy season.
In our experience supporting U.S. firms, the smoothest 14900 workflows use,
- a standing SOP for Pub 936 and Form 14900 lines,
- a naming rule for statements and amortization files,
- a short calculator tab that mirrors lines 1 through 16,
- a checklist that bans partial month balances and forces mixed‑use splits with a note that cites the rule.
Accountably can plug into that system when your team is buried in production. We operate U.S. led offshore delivery with SOP driven execution, structured workpapers, and a layered review model that protects partner time, which is especially useful for high volume compliance tasks like mortgage interest validations. If you want that kind of stability, ask about a seasonal white label review team or a longer term dedicated unit. Use it only if it truly helps your delivery plan, not as a short term band aid.
Our goal is simple, keep your reviewers in strategy, not stuck in balance footings.
FAQs, quick answers you can trust
Do I need Form 14900 if I did not get an IRS letter?
No. Form 14900 is typically mailed during a correspondence exam with the Letter 566 series and is meant to document the same computation you would otherwise do using Publication 936’s worksheet. If you were not asked to submit it, use the Pub 936 worksheet and keep it with your records.
Can I deduct 100 percent of my mortgage interest?
Only if your average balances fall within the qualified loan limit and you itemize on Schedule A. Post‑2017 acquisition debt is capped at $750,000, older acquisition debt uses the $1,000,000 cap, and amounts above the limit reduce what you can deduct.
What is the IRS limit on the mortgage interest deduction in 2025?
For acquisition debt incurred after 12/15/2017, the cap is $750,000 for joint filers, $375,000 for married filing separately. For acquisition debt incurred after 10/13/1987 and before 12/16/2017, the cap is $1,000,000 for joint filers, $500,000 if married filing separately. Grandfathered pre‑1987 debt is treated separately.
How do I compute the average mortgage balance correctly?
Add each month end closing balance or each monthly average balance from your statements, then divide by the number of months the loan was secured by a qualified home. If your lender provides an annual average, you can use that number. Keep the supporting statements.
How do refinances and cash‑outs affect the calculation?
A refinance of acquisition debt generally keeps its character up to the old principal, new cash‑out must be traced to its use. Only the portion used to buy, build, or substantially improve the home counts as acquisition debt for the cap. Track mixed uses and compute separate average balances.
Where do I get the interest number for line 13?
Start with each lender’s Form 1098, add other eligible interest you paid on debts secured by a qualified home that did not generate a 1098. Do not include points on line 13.
Does Form 14900 give me a tax credit?
No. It is a worksheet that documents your deduction calculation for Schedule A. Your result still depends on whether you itemize and how the standard deduction compares in your situation. See Pub 936 for the full rules.
Is mortgage interest no longer deductible?
It is still deductible within the limits above and only if you itemize. The Tax Cuts and Jobs Act changed the caps for newer loans and the larger standard deduction means some households no longer itemize. The underlying deduction remains.
Practical resources and a clean finish
- Use the IRS Form 14900 wizard to complete and submit the worksheet if you received an IRS request. You can also download a PDF from the same page.
- Keep Publication 936 open while you work, it gives the table, definitions, line by line instructions, and examples for mixed‑use debt and average balances.
- Reconcile Form 1098 interest to your statements, note any timing differences, and keep a single PDF of all monthly balances as support.
If your team handles a high volume of these computations and you want predictable turnaround without burning review hours, a disciplined delivery setup helps. Accountably works with U.S. firms that need structured offshore execution, with SOP driven workpapers and layered quality checks that cut partner review time. Use it when it supports your delivery system, not as a replacement for it.
This guide is for education, not legal or tax advice. For complex mixed‑use or refinance cases, work with a qualified tax professional.
Last reviewed, November 6, 2025. Primary sources, IRS Form 14900 wizard and IRS Publication 936 for 2024 with examples referencing 2025 dates and limits, plus current instructions for Form 1098.