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Form 1120X: Amended U.S. Corporation Income Tax Return
IRS Form 1120-X is the Amended U.S. Corporation Income Tax Return used to correct or change elections for a corporation filing with the IRS. Generally, it must be filed within 3 years after the original return was filed.
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IRS Form 1120X - Amended U.S. Corporation Income Tax Return
IRS Form 1120-X is the Amended U.S. Corporation Income Tax Return used to correct or change elections for a corporation filing with the IRS. Generally, it must be filed within 3 years after the original return was filed.
Risk Radar
Scan points- 1Ensure the total adjustments in Part II accurately match the calculations on lines 1 through 4 of Part I.
- 2Filing without entering the correct ending month and year in the space above the EIN.
- 3Not ensuring the totals of column (b) adjustments equal the changes calculated on lines 1 through 4.
- 4Entering an amount as a decrease but failing to place parentheses around it.
- 5Omitting the required explanation for increases or decreases in Part II.
Plain English
This form allows a corporation to fix mistakes on its original tax return or officially change how it calculates certain taxes. Corporations use Form 1120-X when they need to correct income figures or make specific tax elections after the initial filing deadline has passed.
Submission Date
- Filing date: 2025-12-16 08:10:43
- Preparation window: collect IDs, supporting records, and signatures in advance.
- Final review: verify names, dates, and required fields before submission.
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What this form is for
- Use this form when correcting a previously filed Form 1120 (or Form 1120-A) or making elections after the prescribed deadline.
- Do not use Form 1120-X to apply for a quick refund of estimated tax, nor should it be used solely to request IRS approval for a change in accounting method.
- Check Form 4466 instead when applying for a quick refund of estimated tax.
Form selector
Use this form or another form?
Return is amended due to an NOL carryback
The corporation used the claim for a net operating loss (NOL) carryback.
✓ Check Part II explanation.
Return is being amended after a tax audit
The amounts entered on the return reflect adjustments made by the IRS during an examination.
✓ Ensure all changes are noted in Column (b).
Tax year involved a reportable transaction
The corporation participated in a 'reportable transaction' for the tax year being amended, requiring disclosure.
✓ Attach Form 8886 to the filing.
Deadline or filing window
The general filing window requires Form 1120-X be filed within 3 years after the original return was filed. If claiming a refund, the deadline is 2 years after tax payment, whichever date occurs later. A return filed before the due date counts as being filed on that due date.
Checklist
What you need before filling it out
Purpose of Form
Correcting an original Form 1120 or making a post-deadline election · General Instructions
Filer Requirement
Corporation must have already filed its original return · When To File
Adjustment Entry (Column b)
Net increase or net decrease for each line changed in Part I · Form 1120-X, Column (b)
Tax Computation (Line 4)
New amount of tax based on adjusted taxable income from Line 3, Column (c) · Form 1120-X, Line 4
Attachment Requirement
Appropriate schedule, statement, or form supporting an item change · Instructions for Form 1120-X
Tax Shelter Disclosure
Form 8886 (Reportable Transaction Disclosure Statement) · If amending a year with a 'reportable transaction'
Before you submit
- 1The corporation’s name and employer identification number are listed on the form.
- 2The ending month and year of the tax year being amended are entered above the EIN.
- 3All changes made in Part I have a corresponding net increase or decrease noted in Column (b).
- 4Amounts that represent decreases in Part I have parentheses around them in Column (b).
- 5Part II provides a detailed explanation and computation for every change listed in Part I.
- 6Lines 1 through 4 of Column (c) correctly reflect the final adjusted amounts after all changes are applied.
- 7If applicable, Form 8886 is attached to disclose reportable transactions.
How to file this form
- 1Complete Part I by entering the tax year details and recording the original/adjusted figures in Column (a) and the change amount in Column (b).
- 2Calculate and enter the resulting adjusted amounts on lines 1 through 4 of Column (c), ensuring Line 4 reflects the new total tax.
- 3Fill out Part II, detailing the reason for each change made in Part I and showing any supporting computation.
- 4Attach all required schedules or statements, including Form 8886 if applicable, making sure to list the corporation's name and EIN on these attachments.
- 5Mail the completed Form 1120-X and its attachments to the applicable Internal Revenue Service Center where the original return was filed; use a P.O. box number if necessary.
Known limitations
- 1Form 1120-X should not be used to apply for a quick refund of estimated tax; instead, Form 4466 is used.
- 2If the required tentative refund is due to an NOL or capital loss carryback, and less than 1 year has passed since that event, Form 1139 should be used instead of Form 1120-X.
- 3Form 1120-X should not be used when requesting IRS approval for a change in accounting method; Form 3115 is the correct form for this purpose.
Field map
Compact field-by-field guide
Entity Info
2 items
Full legal name of the corporation and its Employer Identification Number.
Current mailing address and date of incorporation.
Income
3 items
Total revenue from business operations before deducting costs.
Direct costs attributable to producing goods sold by the corporation.
Gross receipts minus cost of goods sold and returns/allowances.
Deductions
1 items
Sum of all business expenses including compensation, rent, interest, taxes, and depreciation.
Tax
2 items
Total income minus total deductions.
Tax calculated on taxable income using the applicable corporate tax rate, minus any credits.
Signatures
1 items
An authorized corporate officer must sign and date the return.
Almost done reviewing the fields?
Fillable formOpen in Editor->The current edition is Revision December 2025. For the latest information regarding Form 1120-X and its instructions, filers should refer to IRS.gov/Form1120X.
What changed or needs a fresh check
- Edition date — confirm the revision reads December 2025.
- Mailing address — confirm mailing is directed to an applicable IRS Center (not just the general address).
- Attachment requirement — confirm all necessary supporting schedules, statements, or forms are included.
- Part II detail — confirm that Part II explains every change made in Part I with detailed computation.
- Column (c) check — confirm lines 1 through 4 in Column (c) equal the new adjusted amounts.
Quick Facts
Downloads
After you file
- 1Keep a copy of the filed Form 1120-X.
- 2If attaching supporting documents, include the corporation’s name and employer identification number on them.
- 3When filing as a carryback claim, attach copies of Form 1120 (page 1 and tax computation page) for both the originating year and the carryback year.
- 4It often takes 3 to 4 months for the IRS to process Form 1120-X.
Sources
- SRCInstructions p.1 — Purpose: Use Form 1120-X to correct a Form 1120 or Form 1120-A, or make certain elections after the prescribed deadline.
- SRCInstructions p.1 — Filing Requirement: File Form 1120-X only after the corporation has filed its original return.
- SRCInstructions p.1 — Standard Deadline: Generally, Form 1120-X must be filed within 3 years after the date the corporation filed its original return or within 2 years after paying the tax (if filing a refund), whichever is later.
- SRCInstructions p.1 — Carryback Deadline: A Form 1120-X based on an NOL, capital loss, or general business credit carryback generally must be filed within 3 years after the due date of the return for that year.
- SRCInstructions p.1 — Bad Debt/Worthless Security Deadline: A Form 1120-X based on a bad debt or worthless security must be filed within 7 years after the due date of the return for the tax year it became worthless.
- SRCInstructions p.2 — Where to File: File this form at the applicable Internal Revenue Service Center where the corporation filed its original return.
- SRCInstructions p.1 — Attachments (General): If the corrected amount involves an item requiring a schedule, statement, or form, attach it to Form 1120-X.
- SRCInstructions p.1 — ESBC Specific Rule: If claiming carryback of an unused Eligible Small Business Credit (ESBC), enter “SBJA 2012” at the top of Form 1120-X.
Common confusion points
When must I file this form?
File Form 1120-X only after the corporation has filed its original return.
→ Ensure your filing date is after the original submission.
What is the general deadline to file Form 1120-X?
Generally, it must be filed within 3 years after the corporation filed its original return or within 2 years after paying the tax (if claiming a refund), whichever is later.
→ Check if you are filing based on NOL/capital loss/credit carryback for specific deadlines.
What is the deadline if I am using Form 1120-X for an NOL carryback?
Generally, it must be filed within 3 years after the due date (including extensions) of the return for the tax year involved.
→ Verify this applies to your type of carryback claim.
What is the deadline if I am using Form 1120-X for a bad debt or worthless security?
It must be filed within 7 years after the due date of the return for the tax year in which the item became worthless.
→ This is longer than the standard 3-year rule.
Where do I send this form?
File it at the applicable Internal Revenue Service Center where the corporation filed its original return.
→ Do not send it to the general address (1111 Constitution Ave. NW, IR-6526, Washington, DC 20224) unless directed.
What if my tax year is fiscal?
Enter the ending month and year of the calendar or fiscal year in the space above the employer identification number on Form 1120-X.
Workflow map
Related forms and next steps
Before
Current
After
Often used with
⚠ If something goes wrong
- If using this form as a carryback claim, attach copies of Form 1120 (page 1 and computation page) for support.
Questions about IRS Form 1120X
What is IRS Form 1120X used for?
This form allows a corporation to fix mistakes on its original tax return or officially change how it calculates certain taxes. Corporations use Form 1120-X when they need to correct income figures or make specific tax elections after the initial filing deadline has passed.
Who must file IRS Form 1120X?
A corporation must file IRS Form 1120-X only after that corporation has filed its original return.
What information does IRS Form 1120X require?
Part I collects the core financial details, showing the originally reported amount versus the net change (increase or decrease). The form also gathers information on payments and credits across lines like 5a through 5e.
When is IRS Form 1120X due?
Generally, Form 1120-X must be filed within 3 years after the date the corporation filed its original return. If filing a refund claim, it must be within 2 years after the tax was paid, whichever is later.
Where do I file IRS Form 1120X?
The form must be filed at the applicable Internal Revenue Service Center where the corporation initially filed its original return. If mailing to a P.O. box, show the box number instead of the street address.
How do I complete IRS Form 1120X?
First, enter the ending month and year of the tax year being amended. Then, fill out Part I by listing the original amount (a), the net change (b), and the correct amount (c). Finally, explain all changes in Part II before sending it to the IRS Center.
What happens if IRS Form 1120X is filed incorrectly?
If the filing is incorrect, the IRS may require further processing, and it often takes 3 to 4 months for Form 1120-X to be processed by the agency.
When must I file this form?
File Form 1120-X only after the corporation has filed its original return. Ensure your filing date is after the original submission.
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