Updated October 18, 2026. Quick answer: Form 1040-X is the form you use to correct a return you already filed. Each line has three columns: what the return showed, the change, and the corrected amount. This page walks the form in order and points to the page for each group of lines.
More IRS forms and schedules for individual filers, read line by line: Form 3800 instructions and Form 5405 instructions.
Read box by box from the IRS form text: Form W-2c boxes c to i and Form W-2c Notice to Employee.
Related reading on this site: IRS Notice CP11 (return corrected, amount owed changed), IRS Notice CP13 (return corrected, zero balance), IRS Letter 12C (request for more information) and IRS notices and letters by number.
IRS estate-administration forms, read line by line: Form 1310 Part I, Form 1310 Part II and Form 1310 Part III.
What Form 1040-X does
The instructions open with “If you discover an error after filing your return, you may need to amend your return.” They then say “Use Form 1040-X to correct a previously filed Form 1040, 1040-SR, or 1040-NR, or to change amounts previously adjusted by the IRS.” Each year is its own filing: “File a separate Form 1040-X for each tax year you are amending.”
The instructions also describe what you will need on hand, starting with “A copy of the return you are amending”. The lines on your original return are the starting point for column A. The return itself is explained line by line at Form 1040 line by line.
How the three columns work
The form tells you to enter “the amounts for the return year entered above.” The instructions explain each column. For column A: “Enter the amounts from your original return, unless any of the following apply.” The exceptions are a return you amended before, an audit that changed the return, or an IRS notice that changed it. In those cases “column A needs to reflect the amount to which your originally filed return was adjusted.”
For column B: “Enter the net increase or decrease for each line that you are changing.” “Explain each change in Part II.” For column C, “Add the increase in column B to the amount in column A” or “Subtract the decrease in column B from the amount in column A.” If you leave a line alone, “enter the amount from column A in column C.”
The form in order, section by section
Each row below names the section by its printed heading on the form and links to the page for those lines.
| Section | Lines | Topic | Page |
|---|---|---|---|
| “Income and Deductions” | 1 to 5 | Adjusted gross income, standard or itemized deductions, the qualified business income deduction, the Schedule 1-A deductions and taxable income | Lines 1 to 3 Lines 4a to 5 |
| “Tax Liability” | 6 to 11 | Tax, nonrefundable credits, other taxes and total tax | Lines 6 to 11 |
| Payments | 12 to 17 | Withholding, estimated tax, the earned income credit, refundable credits and total payments | Lines 12 to 17 |
| “Refund or Amount You Owe” | 18 to 23 | Overpayment, amount you owe and refund | Lines 18 to 23 |
| Part I Dependents | 24 to 30 | Changes to dependents | Part I, lines 24 to 30 |
| Parts II and III | Explanations | Why you are filing, and direct deposit for an e-filed form | Parts II and III |
Part I of the form says “Complete this part to change any information relating to your dependents.” Part II says “tell us why you are filing Form 1040-X.” For Part III, the instructions say “you may request your refund be directly deposited into your checking or savings account.”
Which lines to complete
You do not always fill in every line. The instructions say “Complete the lines shown in the charts under Columns A Through C below according to what you are changing.” That chart, under the heading Which Lines To Complete, lists the lines for each kind of change, such as filing status, income, deductions or credits. Read it by name in the instructions rather than relying on a summary here.
The instructions also cover the case where you are only changing information. For that case they list the pieces to complete, including “Complete Part I” when you are changing a dependent.
Where the number comes from
Column A comes from the return you are amending, as filed or as adjusted. The corrected amounts come from the forms and schedules for that same year. The instructions say “See the tax return for the year you are amending to find the corresponding lines on your original return.” The tax computed on line 6 follows the methods of your return year, explained at Form 1040 line 16.
Where it goes next
Form 1040-X does not stand alone. The instructions say “You must place behind your completed paperfiled Form 1040-X a completed and updated Form 1040, 1040-SR, or 1040-NR with the changes you are submitting.” The form’s last result is an amount you owe or an overpayment. Line 20 says “Amount you owe.” and the amount owed is covered at Form 1040 line 37.
Edition and line numbers
This page reads the December 2025 revision of Form 1040-X, Amended U.S. Individual Income Tax Return, and its December 2025 instructions, the current files irs.gov served on 2026-10-18. Form 1040-X is not tied to one tax year: it amends the return year you enter at the top. The form’s own header says “Attach a completed Form 1040, 1040-SR, or 1040-NR, with your changes, for the return year entered below”. The instructions add “These instructions can be used with the December 2025 and later revisions of Form 1040-X, unless later instructions state otherwise.” Check the revision date printed on the form you are filling in and the return year you are amending, and use the line numbers on that form.
Common mistakes
- Combining years on one form. The instructions say “File a separate Form 1040-X for each tax year you are amending.”
- Entering the wrong figures in column A. The instructions say “column A needs to reflect the amount to which your originally filed return was adjusted.” when the return was amended, audited or changed by a notice.
- Leaving the explanation blank. The form says “You must complete Part II on page 2 and explain any changes.”
Related: Form 1040 line by line, Form 1040 line 16, Form 1040 line 37, and Form 1040.
Sources
- Instructions for Form 1040-X, Amended U.S. Individual Income Tax Return (Rev. December 2025): https://www.irs.gov/pub/irs-pdf/i1040x.pdf
- Form 1040-X, Amended U.S. Individual Income Tax Return (Rev. December 2025): https://www.irs.gov/pub/irs-pdf/f1040x.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.