Form 1040-X - Amended U.S. Individual Income Tax Return
Form 1040-X
Amended U.S. Individual Income
Bio: Alistair is a chartered accountant with over 20 years of experience dealing in U.S. and U.K. taxation.
Article
March 2025
10 Minute Read
How to File an Amended U.S. Tax Return Using Form 1040-X
Filing taxes can be a complex task, and sometimes, even after submitting your return, new information comes to light that requires you to make corrections. Whether it’s due to a forgotten credit, a late-arriving W-2, or the introduction of new tax relief legislation, you may need to amend your original tax return. In these cases, the IRS requires you to use Form 1040-X, the official form for filing an amended U.S. individual income tax return.
Reasons You May Need to Amend Your Tax Return
There are many reasons taxpayers find themselves needing to amend a return after it has already been filed. For example, during the COVID-19 pandemic, the IRS announced a wide range of tax relief provisions that were enacted after many individuals had already submitted their returns. If you filed your 2019 tax return without claiming these expanded benefits or more recent disaster-related tax relief, you may still be eligible to take advantage of them by filing an amended return.
In other cases, the need to amend may come from something more routine—such as discovering that you received an additional W-2 or 1099 form after filing your return, or realizing that you failed to claim tax credits you were eligible for. These credits might include the Child Tax Credit, the Credit for Other Dependents, or other deductions that could significantly reduce your tax bill or increase your refund.
You may also need to amend your return if you initially chose the wrong filing status. For instance, if you filed jointly but later determine you should have filed separately, or vice versa, the only way to correct that is through an amended return. Some taxpayers amend their returns to carry a tax credit or loss from a later year back to an earlier one, or to claim a benefit that was made available through newly enacted legislation after the original return was submitted.
How Form 1040-X Works
Form 1040-X is structured to clearly show the changes you're making to your original tax return. It includes three key columns that allow you to display the original figures as reported, the net change you're making, and the corrected amounts that should now apply. This clear comparison helps the IRS understand what changes are being made and why.
Part III of the form, titled "Explanation of Changes," is where you provide a written statement explaining the reasons for your amendment. This section is important because it allows you to detail the specific issues or events that led to the changes. For example, you might explain that you received a late W-2 from a former employer, discovered a missed credit for dependent care expenses, or realized that your filing status was incorrect. Being thorough and clear in this section helps the IRS process your amended return more efficiently and reduces the likelihood of questions or delays.
It’s also worth noting that beginning in January 2020, the IRS officially began labeling the form as “1040-X” (adding a hyphen). If you come across older documents or references to “1040X,” they are referring to the same form—just an earlier version of its formatting.
Taxpayers who missed previous filings or have undeclared foreign income can minimize penalties by using IRS and HMRC voluntary disclosure programs:
Filing an Amended Return: Step-by-Step
1. Completing Form 1040-X
The first step in amending your tax return is obtaining and filling out IRS Form 1040-X, which is the official document used for making corrections to a previously filed individual income tax return. Unlike the original return, which can often be submitted online using e-filing services, Form 1040-X must currently be filed as a paper return.
You can complete the form either manually by printing it out and writing in your information or by using tax preparation software that supports amended returns. Many online platforms now allow you to complete Form 1040-X digitally and print it when you’re done.
The form includes three primary columns: one for the original figures reported on your initial return, a second for the net change you’re making, and a third for the new, corrected amounts. Be precise when updating these figures, and double-check your calculations to avoid further amendments.
Don’t forget about Part III – Explanation of Changes, a written section where you must clearly explain why you are amending the return. Be specific. For example, note whether you received an additional W-2, discovered a missed deduction, or are claiming a new credit made available through recent legislation. A vague explanation can lead to delays or IRS inquiries.
2. Attaching the Required Supporting Documentation
Along with Form 1040-X, it is essential to include all supporting documentation that backs up the changes you’re making. This may include:
- A newly received or corrected W-2 or 1099 form
- Additional or updated tax schedules (such as Schedule A for itemized deductions or Schedule C for self-employment income)
- Forms related to credits or deductions, like the Child Tax Credit
- Any other documentation that supports your reason for the amendment
Many processing delays happen because taxpayers forget to include these attachments. Think of Form 1040-X as a new version of your return—it needs to stand on its own and include everything the IRS will need to fully assess your corrections.
If your changes involve multiple tax years, you will need to file a separate Form 1040-X for each year, with appropriate documentation for each. Make sure that each return is clearly labeled and sent in its own envelope to avoid confusion or misrouting.
3. Mailing the Amended Return
Once your amended return is completed and the supporting documents are assembled, the next step is mailing it to the IRS. The correct mailing address depends on your location and whether or not you’re including a payment with your return. You can find the correct address in the instructions provided with Form 1040-X or on the IRS website.
Use a reliable mail service with tracking or certified delivery to confirm that your return has been received by the IRS. This is especially important if your amendment involves a large refund or significant changes to your tax obligations.
Currently, the IRS does not accept e-filed Form 1040-X for all tax years, so even if your original return was filed electronically, the amended version still needs to be mailed in most cases. However, keep an eye on IRS updates, as electronic filing may be available for more amended returns in the near future.
4. Submitting Additional Tax Payments
If your amended return results in a higher tax liability, meaning you owe more than what was calculated on your original return, it’s best to pay the additional tax when you file. This helps avoid further interest charges and late payment penalties.
The IRS offers several convenient methods for submitting payments:
- Direct Pay from your checking or savings account
- IRS2Go mobile app
- Credit or debit card payments via authorized payment processors
- Mailing a check or money order along with your 1040-X form
5. Receiving a Refund from an Amended Return
If the changes on your Form 1040-X entitle you to a refund, the IRS will process and issue it after they complete their review. If you have included your U.S. bank account information—specifically the routing and account number—on the form, the IRS will typically issue the refund via direct deposit, which is faster and more secure than receiving a paper check.
However, if you do not have a U.S.-based bank account or did not include direct deposit details, the IRS will mail a paper check to the address listed on your amended return. This process may take longer, especially for international filers or those living abroad, so it’s critical to make sure your mailing address is current and accurate.
6. Keeping Copies for Your Records
After you’ve mailed your amended return, be sure to keep copies of everything for your records. This includes the completed Form 1040-X, all supporting documents, and any confirmation of mailing or payments made. These documents may be useful if the IRS contacts you for further clarification or if you need to reference them in future filings.
When You Can and Should File Form 1040-X
An amended tax return can only be submitted after you have filed your original return. Timing matters because the IRS has strict limits on when you can make amendments. Generally, you must file Form 1040-X within three years from the date you filed the original return, including any extensions. Alternatively, you may also file within two years from the date you paid the tax, if that date is later.
There are nuances to be aware of when calculating these deadlines. For example, if you filed your return early, such as on March 1 for a calendar-year return, the IRS considers it filed on the official due date, which is typically April 15. But if you filed under an extension—for example, expats who may have until June 15—and your return was received on May 1, then your filing date is considered to be May 1. Understanding these rules can help ensure your amended return is submitted within the allowable time frame.
How to Track the Status of Your Amended Return
Once you’ve mailed your amended return, it doesn’t get processed overnight. The IRS advises allowing 8 to 12 weeks for processing. During this time, you may be eager to know where your return stands. Fortunately, the IRS offers an online tool called “Where’s My Amended Return?”, available on their official website.
It typically takes around three weeks from the time you mail your amended return before it appears in the IRS system. Once it's there, you can track its status by entering a few key pieces of information: your taxpayer identification number (usually your Social Security Number), your date of birth, and your current ZIP or postal code. The tool will show whether your return is being processed, whether additional information is needed, or if it has been completed.
What to Do Next
If you believe you need to file an amended U.S. tax return, it’s important to act in a timely manner and ensure that all corrections are accurately documented. While many taxpayers handle this process on their own, it can be especially beneficial to consult with a professional—particularly if you are a U.S. expat dealing with international income, foreign tax credits, or special exclusions.
Our team of experienced U.S. expat tax accountants and preparers is here to help you review your situation, determine whether an amendment is necessary, and guide you through every step of the process. Filing an amended return doesn’t have to be stressful—get in touch with us today for expert advice and personalized support.