! otherwise — Instruction 1040-X — Instructions for Form

CAUTION lines on Form 1040-X, as discussed under Line

Instructions , later.

Additional Medicare Tax. If your Medicare wages, RRTA compensation, or self-employment income is adjusted, you may need to correct your liability, if any, for Additional Medicare Tax. When correcting Additional Medicare Tax liability, attach to Form 1040-X a corrected Form 8959, and, if correcting Medicare wages or RRTA compensation, attach Form W-2, Wage and Tax Statement, or Form W-2c, Corrected Wage and Tax Statement. For more information, see the Instructions for Form 8959.

Bipartisan Budget Act of 2015 (BBA) Partner Modification Amended Return. A partner in a BBA Partnership that has requested modification type “Amended Returns of Partners Under IRC Section 6225(c)(2)(A)” files a partner modification amended return. A partner modification amended return includes a partner amended return for the partner's first affected year and any prior or subsequent tax years impacted as a result of taking the partnership adjustments into account in the partner's first affected year. Such returns must include the payment of all tax, penalties, additions to tax, and interest due as a result of taking into account all partnership adjustments properly allocated to the partner, and including adjustments to any tax attributes affected by taking into account the partnership adjustments. You must write “BBA Partner Modification Amended Return” at the top of page 1 of all partner modification amended returns being filed (for e-filed amended returns, attach a statement). See Form 8982 for additional information and instructions.

Attach a statement to each partner modification amended return that contains the following information.

Name of source partnership (which is the audited partnership requesting modification and from which you are receiving adjustments).
Taxpayer Identification number (TIN) of the source partnership.
Audit control number—obtain this number from the partnership representative of the source partnership.

4 Instructions for Form 1040-X (Rev. December 2025)

reflected on an amended return for the partner's first affected year. Do not include the income tax changes on the Form 1040-X. Instead, the Form 1040-X should reflect the original and correct amounts as originally reported (or as previously amended) on the Form 1040 such that there is no change between the original and correct amounts on lines 1–8. Complete any applicable forms for the non-income taxes such as the Schedule SE (Form 1040) (for self-employment taxes) or Form 8960 (for net investment income tax) including the adjustments reflected on the Form 8986 and figure the adjusted non-income taxes using the adjusted numbers. Report the corrected non-income taxes on line 10 of the Form 1040-X and figure the additional amount owed. The amended return should include a statement that explains how the change to non-income tax was figured, and the source of the adjustment in Part II of the Form 1040-X. See Form 8978 for additional information and instructions.

Qualified Opportunity Investment. Attach to the back of Form 1040-X any Form 8997, Initial and Annual Statement of Qualified Opportunity Fund (QOF) Investments, that supports changes made on this return if qualified investments were held during the year.

Carryback claim—NOL. Write or type “Carryback Claim” at the top of page 1 of Form 1040-X. Attach a computation of your NOL using Schedule A (Form 1045) and a computation of any NOL carryover using Schedule B (Form 1045). A refund based on an NOL doesn’t include a refund of self-employment tax reported on Form 1040-X, line 10. Generally, interest won’t be paid on any NOL refund shown on an amended return processed within 45 days of receipt. For details, see Pub. 536, Net Operating Losses (NOLs) for Individuals, Estates, and Trusts.

Carryback claim—credits and other losses. Write or type “Carryback Claim” at the top of page 1 of Form 1040-X. Attach copies of the following.

Both pages of Form 1040 and Schedules A and D, if applicable, for the year in which the loss or credit originated. Write or type “Attachment to Form 1040-X—Copy Only—Do Not Process” at the top of these forms.
Any Schedules K-1 or K-3 you received from any partnership, S corporation, estate, or trust for the year of the loss or credit that contributed to the loss or credit carryback.
Any form or schedule from which the carryback results, such as Form 3800, General Business Credit; Form 1116; Form 6781, Gains and Losses From Section 1256 Contracts and Straddles; Form 4684, Casualties and Thefts; or Schedule C or F (Form 1040).
Forms or schedules for items refigured in the carryback year, such as Form 6251, Alternative Minimum Tax—Individuals; Form 3800; Schedule A (Form 1040); Schedule A (Form 1040-NR); or Form 8962, Premium Tax Credit.

Carryback claim—change in filing status. If you were married and you didn’t have the same filing status (married filing jointly or married filing separately) for all of the years involved in figuring the loss or credit carryback, you may have to allocate income, deductions, and credits. For details, see the publication for the type of carryback you are claiming. For example, for NOL carrybacks, see Pub. 536.

Section 174A. P.L. 119-21 added section 174A, which pertains to domestic research and experimental expenditures. Section 174A(f)(2) allows an election to deduct certain unamortized amounts paid or incurred in tax years beginning after 2021 and before 2025. For more information about section 174A, see Revenue Procedure 2025-28.

Casualty loss from a federally declared disaster. If you have a casualty loss attributable to a federally declared disaster, you may be able to elect to deduct the loss in the tax year immediately before the tax year the loss was sustained. The

election must be made by filing your return or amended return for the preceding year, and claiming your disaster loss on it, no later than 6 months after the due date for filing your original return (without extensions) for the year in which the loss was sustained. For more information about this election, see the Instructions for Form 4684; and Rev. Proc. 2016-53, 2016-44 I.R.B. 530, available at IRS.gov/irb/2016-44_IRB#RP-2016-53 .

Deceased taxpayer. If filing Form 1040-X for a deceased taxpayer, write or type “Deceased,” the deceased taxpayer's name, and the date of death across the top of Form 1040-X, page 1.

If you originally filed a joint return and you are filing Form 1040-X to claim a refund with respect to that joint return as a surviving spouse, sign the return and enter “Filing as surviving spouse” in the area where you sign the return. If someone else is the personal representative, they must also sign.

Claiming a refund for a deceased taxpayer. If you are filing a joint return as a surviving spouse, you only need to file Form 1040-X to claim the refund. If you are a court-appointed personal representative or any other person claiming the refund, file Form 1040-X and attach Form 1310, Statement of Person Claiming Refund Due a Deceased Taxpayer, and any other information required by its instructions. For more details, see Pub. 559, Survivors, Executors, and Administrators.

Household employment taxes. If you are correcting an error in the employment taxes for household employees that you reported on a Schedule H previously filed with Form 1040, 1040-SR, 1040-NR, or 1040-SS, attach a corrected Schedule H and include in Part II of Form 1040-X the date the error was discovered. If you filed Formulario 1040-PR, file a Form 1040-X and attach a corrected Anexo H-PR. If you owe tax, pay in full with this return. If you are changing the wages paid to an employee for whom you filed Form W-2, you must also file Form W-2c, and Form W-3c, Transmittal of Corrected Wage and Tax Statements, with the Social Security Administration. For more information, see Pub. 926 for the appropriate year.

Injured spouse claim. If you filed a Form 8379 and are filing a Form 1040-X to request an additional refund, and you don’t want your portion of the overpayment to be applied (offset) against your spouse's past-due obligation(s), complete and attach another Form 8379 to allocate the additional refund.

Signing your minor child's return. If your minor child can’t sign the return, either parent can sign the child's name in the space provided. Enter “By (your signature), parent for minor child.”

Tax shelters. If you are amending your return to disclose information for a reportable transaction in which you participated, attach Form 8886, Reportable Transaction Disclosure Statement.

Wrongfully incarcerated individuals. Certain amounts you receive due to wrongful incarceration may be excluded from gross income. If you included these amounts in income in a prior year, you may be able to amend your return to claim a refund or credit against your tax. For the latest information, go to IRS.gov/ newsroom/irs-updates-frequently-asked-questions-related-to- wrongful-incarceration .