What IRS Form 1120X (2015) Is For
IRS Form 1120X (2015) is an amended corporation income tax return used by corporations to correct errors or omissions on their original Form 1120 for the 2015 tax year. It allows a corporation that filed Form 1120 to adjust taxable income, report additional income, or claim missed deductions and tax credits after the original return was filed, and to make certain elections after the prescribed deadline. (Other corporate returns, such as Forms 1120-F, 1120-H and 1120-RIC, are corrected with an amended version of that same form, not Form 1120-X.)
Corporations file an amended return when their tax attributes, tax liability, or net income change due to accounting adjustments, amended schedules, or corrected transactions. The IRS provides instructions to ensure that corporations determine whether the correction falls within the applicable statute of limitations, which is generally within 3 years after the date the corporation filed its original return or within 2 years after the date it paid the tax, whichever is later (a return filed before the due date is considered filed on the due date). Claims based on a net operating loss, capital loss or credit carryback are generally due within 3 years after the due date, including extensions, of the loss or credit year, and claims for bad debts or worthless securities have a 7-year period.
When You’d Use Form 1120X for 2015 (Late or Amended Filing)
You’d use IRS Form 1120X (2015) if your corporation filed a 2015 tax return and later discovered errors that affect income tax or corporate income tax owed. This applies when income, deductions, or credits were miscalculated. You may also need to file when the IRS sends a notice about discrepancies, or when estimated tax payments and other returns from the same tax year reveal inconsistencies.
Corporations may need to file an amended return when they discover unreported business income, incorrect carrybacks, or missed corporate elections. Refund claims must be submitted before the prescribed deadline—generally within 3 years after the date the corporation filed its original return or within 2 years after the date it paid the tax, whichever is later. Corporations should ensure the return is mailed to the same service center as the original tax return.
For complete details on wage reporting, withholdings, and unemployment tax filings, see our guide to Business Income Tax Forms.
Key Rules Specific to the 2015 Tax Year
- Failure-to-File Penalty: The IRS charges 5% of the unpaid tax per month, up to a maximum of 25%.
- Minimum Late Filing Penalty: If the original 2015 Form 1120 was filed more than 60 days late, the minimum failure-to-file penalty is the smaller of $205 or 100% of the tax due; filing Form 1120X does not itself trigger this penalty.
- Failure-to-Pay Penalty: The IRS adds 0.5% per month on any unpaid income tax, up to 25%.
- Corporate Tax Rates: 2015 corporate rates ranged from 15% to 35%, with 39% and 38% bracket rates that phased out the lower rates.
- Electronic Filing Rules: Corporations with $10 million in assets and 250 or more returns were required to e-file.
- Calendar Year vs. Fiscal Year: Calendar-year filers had to align amendments with the correct tax year.
Mail Form 1120-X to the IRS center where the corporation filed its original return.
Step-by-Step (High Level)
- Gather Original Records: Collect your 2015 Form 1120, IRS transcripts, and applicable schedules.
- Complete Form 1120X: Enter corrected figures in the three-column layout and provide explanations in Part II.
- Attach Supporting Documentation: Include schedules showing revised gross income, business deductions, or credits.
- Submit to the Correct Address: Mail the return to the IRS center where your corporation filed the original return.
- Track Payment and Refund Status: If you are claiming a refund, monitor the processing and payment dates.
- Retain Copies: Keep the amended return, supporting documents, and proof of mailing for at least three tax years.
Learn more about federal tax filing through our IRS Form Help Center.
Common Mistakes and How to Avoid Them
- Incomplete Explanations: Always explain every change in Part II, especially those affecting income, deductions, or tax attributes.
- Incorrect Filing Address: Send your return to the same service center that processed your original return to prevent delays.
- Missing Documentation: Attach all applicable schedules and statements, particularly for certain corporations involved in foreign transactions.
- Math Errors: Recheck taxable income and verify that Column C accurately reflects your updated tax computation.
- Filing Too Early: File Form 1120-X only after the corporation has filed its original return.
- Overlooking Carryback Rules: If Form 1120-X is used as a carryback claim, attach copies of Form 1120 page 1 and the tax computation page for both the loss or credit year and the carryback year, marked 'Copy Only—Do Not Process.'
- Incorrect Payment Handling: Pay tax owed immediately to minimize interest and penalties on unpaid balances.
Learn more about how to avoid business tax problems in our guide on How to File and Avoid Penalties.
What Happens After You File
The IRS typically takes 3–4 months to process Form 1120X. The return is reviewed for accuracy, ensuring all applicable schedules and credits are properly claimed. If additional tax is due, the IRS will issue a notice and calculate interest from the original due date. Refunds include interest where applicable. Corporations may appeal IRS adjustments.
FAQs
How long do I have to file IRS Form 1120X (2015) for an amended return?
Corporations must file Form 1120X within three years of the original filing or two years after tax payment. For 2015 corporate returns, the general due date was March 15, 2016, so for a return filed by that date, the general refund deadline was March 15, 2019. Amended returns filed after this period generally cannot claim refunds or credits for prior income tax.
Will I owe additional corporate income tax when filing an amended return?
Filing an amended return may increase or decrease corporate income tax liability depending on your net income, deductions, and credits. The IRS applies penalties and interest from the original due date if additional tax is due. Promptly paying any difference helps limit interest and the failure-to-pay penalty.
Can I include new business deductions or changes from a controlled group?
Yes, corporations may amend returns to include eligible business deductions or adjustments within a controlled group structure. This may also apply to relationships with affiliated or parent corporations. Be sure to include full explanations and supporting schedules when submitting your amended return.
How does Form 1120 differ from Form 1120X?
Form 1120 is the original corporate income tax return, while Form 1120X is the amended version for corrections. Mail Form 1120-X to the IRS center where the corporation filed its original return. Corporate taxpayers should ensure all pages are complete and signed before mailing.
Can superseding returns be filed instead of an amended return?
A superseding return replaces an original tax return filed before the due date or automatic extension deadline. After that date, only an amended return using Form 1120X may be filed. Corporations must determine whether their submission qualifies as superseding or amended to avoid IRS rejection.
For more on Form 1120-X, see the IRS About Form 1120-X page.
