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 domestic corporations and foreign corporations to adjust taxable income, report additional income, or claim missed deductions and tax credits after the original return was filed by the IRS. The form also applies to certain corporations that need to correct regulated investment company filings or update business deductions for accurate reporting of corporate income tax returns.
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 either three years from the original filing date or two years from the date of payment.
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 to corporations that pay tax on gross income, deductions, or credits that 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.
Certain corporations are required 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—typically within three years of the original filing or two years from the date of payment. 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% per year.
- Minimum Late Filing Penalty: A $135 minimum applies if filed more than 60 days late.
- Failure-to-Pay Penalty: The IRS adds 0.5% per month on any unpaid income tax.
- Corporate Tax Rates: 2015 rates ranged from 15% to 35% of taxable income.
- Electronic Filing Rules: Corporations with $10 million in assets and 250 or more returns were required to e-file.
- Affordable Care Act Requirements: Certain transactions and employer mandates applied to large corporations and financial institutions.
- Calendar Year vs. Fiscal Year: Calendar-year filers had to align amendments with the correct tax year.
These rules also covered certain elections made by homeowners' associations, foreign entities, parent corporations, and controlled groups that filed consolidated returns. The IRS required paper forms for superseding returns and prohibited e-filing for Form 1120X.
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: Wait until your original tax return is fully processed before filing an amended return.
- Overlooking Carryback Rules: If you are claiming a credit or refund for prior tax years that began before 2015, attach the supporting forms.
- 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 are paid by check or direct deposit, with interest where applicable. Corporations may appeal IRS adjustments, and certain elections can be reconsidered through the Appeals Office or the Tax Court.
Corporations should note that IRS pages related to Form 1120X often include a locked padlock icon for secure filing instructions. Always verify the latest guidance under “page last reviewed or updated” to ensure current-year compliance for corporate returns or superseding returns.
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, making the final deadline 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 reduce late filing and failure-to-pay penalties.
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 when e-filing corporate returns?
Form 1120 is the original corporate income tax return, while Form 1120X is the amended version for corrections. Although Form 1120 may be e-filed, the IRS requires paper filing for Form 1120X. 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.
