If you look back on a previous tax return and discover you've made a mistake, then you can always correct it. Use Form 1040-X, Amended U.S. Individual Income Tax Return to file an amended tax return with the necessary changes or adjustments.
What Can I Change with Form 1040-X?
Form 1040-X should be used to correct any inaccurate information that was reported on your original tax return. A few examples include:
- Filing status
- Total income
There’s no need to file an amended return if you forgot certain forms such as a W-2 or one of the Schedules. If any of these documents are missing and needed by the IRS, then they will send you a letter requesting them.
Note that after filing Form 1040-X and having it accepted by the IRS, it becomes the new tax return for that year. Take note of key values such as a different AGI (adjusted gross income). Going forward when the IRS asks for your previous AGI to verify your identity, you’ll want to use the most up-to-date information.
Can I E-File Form 1040-X?
Online, this can only be done for tax returns beginning with the year 2019. Unfortunately, this is when the IRS set up a new system for processing amended returns, so amended returns for tax years before 2019 must be sent in by mail.
Don't Forget to Amend Your State Return
More than likely if you make an adjustment to your federal tax return, then you'll also need to update your state tax return for the corresponding year.
To do this, check your state's Treasury Department website for the necessary form. It will be up to the state if this amended return can be e-filed or must be sent in by mail. When sending in your amended state return, you may be required to attach a copy of your federal Form 1040-X so the state processors will understand the root cause of the change.