Updated October 17, 2026. Quick answer: Line 20 is the deduction for contributions to a traditional IRA. You do not copy it from a statement. You work it out on the IRA Deduction Worksheet in the Form 1040 instructions, and the result goes on line 20. Your IRA custodian’s statement shows the contributions to use, and a retirement plan at work can reduce or eliminate the deduction.
Business use of your home (Form 8829), the saver’s credit (Form 8880), clean vehicle credits (Form 8936) and amended returns (Form 1040-X), read line by line: Form 8880 line 12, Form 8936 Part I and Form 1040-X lines 1 to 3.
IRS worksheets from the 2025 Form 1040 instructions, read line by line: IRA Deduction Worksheet.
Form 8606 and Form 8889 for 2025, read line by line: Form 8606 line 1 and Form 8606 lines 3, 4 and 5.
What line 20 asks for
The form’s caption reads “IRA deduction. If you are married filing separately and lived apart from your spouse for the entire year”, followed by the words check here. The instructions open with a reporting rule for contributions you cannot deduct: “If you made any nondeductible contributions to a traditional individual retirement arrangement (IRA) for 2025, you must report them on Form 8606.” That form is explained on the Form 8606 page.
Where the number comes from
The instructions say “If you made contributions to a traditional IRA for 2025, you may be able to take an IRA deduction. But you, or your spouse if filing a joint return, must have had earned income to do so.” They also say how to find the amount: “Use the IRA Deduction Worksheet to figure the amount, if any, of your IRA deduction.” The worksheet is in the Form 1040 instructions, and this page does not copy its cells. For the contributions themselves, the instructions say “A statement should be sent to you by June 1, 2026, that shows all contributions to your traditional IRA for 2025.”
On earned income, the instructions say “For IRA purposes, earned income includes alimony and separate maintenance payments reported on Schedule 1, line 2a.” For limits on how much can go into an IRA at all, see the page on the IRA contribution limit.
What does not go on line 20
The instructions list several things to read before filling in the worksheet. Among them: “You can’t deduct contributions to a Roth IRA.” And: “You can’t deduct elective deferrals to a 401(k) plan, 403(b) plan, section 457 plan, SIMPLE IRA plan, or the federal Thrift Savings Plan.” For a joint return they say “You must file a joint return to deduct contributions to your spouse’s IRA.” and “Enter the total IRA deduction for you and your spouse on line 20.”
If you were covered by a retirement plan
The instructions warn that if you were covered by a retirement plan “at work or through selfemployment, your IRA deduction may be reduced or eliminated.” To tell whether you were covered at work, they say “box 13 of your Form W-2 should be checked if you were covered by a plan at work even if you weren’t vested in the plan.” The dollar amounts that apply are in the worksheet, so check them there for your own filing status.
The married filing separately box
The checkbox on line 20 is covered by this direction: “If you are married filing separately and you lived apart from your spouse for all of 2025, check the box on line 20.” The consequence of leaving it unchecked is stated this way: “If you don’t check the box on line 20, you may get a math error notice from the IRS.”
Where it goes next
Line 20 is one of the lines added on line 26. The caption for line 26 reads “Add lines 11 through 23 and 25.” and then “Enter here and on Form 1040, 1040-SR, or 1040-NR, line 10”. See Schedule 1 lines 25 and 26 for the totals and the Schedule 1 (Form 1040) page for the whole schedule.
Edition and line numbers
This page reads the 2025 Schedule 1 (Form 1040) and the 2025 Form 1040 instructions, the current files irs.gov served on 2026-10-17. They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, or 1040-NR.” Schedule 1 has no separate instructions booklet. Its line instructions sit inside the Form 1040 instructions, under the heading “Instructions for Schedule 1”. 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
- Deducting a Roth contribution. The instructions say “You can’t deduct contributions to a Roth IRA.”
- Counting a 401(k) deferral as an IRA deduction. The instructions say “You can’t deduct elective deferrals to a 401(k) plan, 403(b) plan, section 457 plan, SIMPLE IRA plan, or the federal Thrift Savings Plan.”
- Skipping the line 20 checkbox when it applies. The instructions say “If you don’t check the box on line 20, you may get a math error notice from the IRS.”
Related: Form 8606, IRA contribution limit, and Form 1040.
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- Instructions for Form 1040 and Form 1040-SR (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Schedule 1 (Form 1040), Additional Income and Adjustments to Income (2025): https://www.irs.gov/pub/irs-pdf/f1040s1.pdf
Read from the IRS documents linked above on October 17, 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.