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How to File a Missouri Tax Amendment

If you need to change or amend an accepted Missouri State Income Tax Return for the current or previous Tax Year, you need to complete Form MO-1040 for the appropriate Tax Year. Form MO-1040 is a Form used for the Tax Amendment. You can prepare a 2021 Missouri Tax Amendment on eFile.com, however you cannot submit it electronically. In comparison, the IRS requires a different Form - Form 1040X - to amend an IRS return (do not use Form 1040 for an IRS Amendment). 

The IRS might send you a notification to change an error on your Return, or you might have discovered an error. If you or the IRS amended or changed one of your IRS Tax Return(s), the IRS will report this to the Missouri Tax Agency, thus you should file a Missouri Amendment within one year.

File a 2021 Missouri Tax Amendment
You cannot eFile a MO Tax Amendment anywhere, except mail it in. However, you can prepare it here on eFile.com.
Option 1: Sign into your eFile.com account, modify your Return and download/print the MO Form MO-1040 under My Account. Check the "Amended Return" box, sign the form, and mail it to the address below.
Option 2: If you don't have an eFile.com account follow the step by step instruction on how to prepare a tax return/amendment.
Option 3: If you want to do the math on your own paper return then complete, sign MO Form MO-1040 - Print, Mail the Form to MO Tax Department to:
Department of Revenue
P.O. Box 3370
Jefferson City, MO 65105-3370
MO Tax Amendment Form MO-1040
This Form can be used to file a: Tax Return, Tax Amendment, Change of Address. Check the "Amended Return" box on the Form.
Step 1: Download, Complete Form MO-1040 for the appropriate Tax Year below.
Step 2: Sign, Mail Your Amended Return to the address listed above.
Tax Year 2021 only: Prepare online on eFile.com until Oct. 15, 2022. When done Print, Sign and Mail in - not eFile - Your Tax Amendment, Address Change, etc.
After Oct. 15 Prepare, Print, Sign and Mail-In - see address above - your Tax Year 2021 - Form MO-1040.
How to correct a rejected Tax Return
If your MO Tax Return was rejected by the MO Tax Agency - not eFile.com - instructions on how to correct a rejected Missouri Tax Return.
Check Your MO Tax Amendment Status
1. Call the MO Department of Revenue at 573-751-3505.
2. Contact the MO Department of Revenue
Missouri Refund Deadlines
A. Three years from the due date of the original tax year return, including valid filing extensions.
B. One year from the final determination of the amended federal return or federal change, whichever is later, provided that the allowable refund is not more than the decrease in Missouri tax attributable to the federal change or correction.
C. Two years from the payment of an assessment, provided the amended return raises issues relating only to the prior assessment and the refund does not exceed the amount of tax paid on the prior assessment.
D. Two years from the filing of an amended Missouri return resulting in the payment of additional tax, provided that the current amended return raises issues relating solely to the prior amended return and that the refund does not exceed the amount of the tax payment made as a result of the prior amended return.
Additional Missouri Tax Income Taxes Deadlines
Missouri Income Tax Penalties
Find out how Missouri Late Filing and Late Payment Penalties are calculated.
For IRS Tax and Late Filing Penalties we have an easy to use tool: The PENALTYucator.
File an IRS Tax Amendment by Tax Year
Instructions on how to prepare an IRS Tax Amendment on eFile.com, however the IRS does not accept Tax Amendments electronically.