IRS Form 1120X (2017): Amended Corporation Tax Return
What IRS Form 1120X (2017) Is For
Corporations use IRS Form 1120X (2017) to correct or amend an original return filed on Form 1120, the U.S. Corporation Income Tax Return. This amended return allows corporations to correct errors, claim missed credits, or adjust figures that impact their federal return and overall tax liability. Filing ensures compliance with IRS requirements and prevents unnecessary penalties or interest.
Corporations often file when they receive IRS notices about incorrect income, deductions, or other items. A clear explanation in Part III, along with supporting documents, is required to validate the changes. Each form must be signed, dated, and mailed with attachments to the correct IRS address listed on the IRS website.
When You’d Use Form 1120X for 2017 (Late or Amended Filing)
You should file Form 1120X for 2017 if your corporation discovered math mistakes, omitted income, or missed deductions on your original tax return. Although refund requests for 2017 generally expired in April or May 2021, you must still amend if you owe additional tax. Late filings remain applicable for corporations needing to correct prior errors.
Amending helps avoid increased penalties, ensures accurate federal and state returns, and updates the IRS record. Refunds can no longer be claimed; however, any outstanding balance must be settled with interest to prevent further charges. Payment may be made by check or through the IRS online system, which is identified by the locked padlock icon to confirm a secure transaction.
Key Rules Specific to 2017
The 2017 tax year included special transition rules under the Tax Cuts and Jobs Act (TCJA).
- Blended Tax Rates: Fiscal-year corporations covering the 2017–2018 period were required to apply blended tax rates on their returns.
- Section 965 Transition Tax: Deferred foreign income was subject to an additional transition tax.
- Late-Filing Penalties: The minimum penalty was $210 or the tax due, whichever was smaller, for returns filed more than 60 days after the due date.
- Refund Deadline: The refund window for 2017 returns closed in May 2021, excluding any COVID-19-related extensions.
Step-by-Step (High Level)
- Gather Tax Transcripts: Request transcripts using Form 4506-T to confirm what the IRS has on file.
- Complete the Amended Form: Enter original and corrected amounts, net changes, and a full explanation in Part III.
- Attach Supporting Documents: Include revised schedules, statements, and forms showing all corrections.
- Mail Only: Form 1120X must be filed on paper; e-filing and e-filed submissions aren’t allowed for 2017. Send by certified mail to the applicable IRS service center.
- Keep Copies: Keep copies of all documents and attachments. Processing an amended return typically takes three to four months from the date it is filed.
Common Mistakes and How to Avoid Them
- Unclear Explanations: Each amended return must include a detailed reason for the change.
- Omitting Attachments: Always attach updated schedules, forms, and documentation that support the corrections.
- Filing Too Early: Wait until the original return has been fully processed before sending Form 1120X.
- Incorrect Penalty Calculations: The IRS calculates penalties and interest automatically; avoid guessing amounts.
- Ignoring State Returns: State returns often require amendment when a federal return is changed.
- Missing Deadlines: Refund claims are closed, but filings that correct underpaid tax remain required.
What Happens After You File
After you file, the IRS usually takes several months to process amended returns. The agency may send notices confirming receipt, adjustments, or requests for additional details. If tax is owed, interest and penalties will apply from the original due date in March 2018.
If unable to pay in full, corporations can apply for a payment plan using Form 9465 or through the IRS website. Payment reduces penalties but doesn’t stop interest from accruing. Once the IRS updates its records, you’ll receive confirmation of changes. Keep all correspondence and copies for at least three years after filing to support future audits or compliance checks.
FAQs
Can I still file IRS Form 1120X (2017) for a corporation's income tax return?
Yes, corporations can still file Form 1120X (2017) to amend an original return, even though the refund period expired. These amended returns are used to correct errors and to pay any additional tax that is due. Filing ensures compliance with IRS rules and prevents the accumulation of ongoing penalties or interest.
How do penalties and interest apply to an amended return?
Penalties apply to any unpaid tax from the original due date, and interest continues until paid. If you can’t pay immediately, you may request a payment plan using Form 9465. This option reduces monthly penalty rates and helps manage outstanding debt over time while maintaining good standing with the IRS.
Do I need to include tax return transcripts when submitting an amended return?
It’s not required, but obtaining tax transcripts helps ensure all information matches the IRS record. Request them before filing to avoid errors or duplicate changes. Use Form 4506-T or the IRS secure online portal (noted by the locked padlock icon) to request a copy of your transcripts or other forms.
Should I amend my state returns if I amend my federal return?
Yes, most states require corporations to file corresponding state returns when the federal return is amended. Failing to file can lead to additional penalties, interest, or discrepancies. Always check with your state revenue agency to learn deadlines, required documents, and the applicable mailing address.
Can Form 1120 be e-filed for amended returns?
No, amended returns for 2017 cannot be e-filed or submitted electronically. Each form must be completed on paper, signed, and mailed with all attachments. Choose a secure delivery method, such as certified mail, to ensure your documents arrive at the IRS service center safely and on time.
