How to Amend a Missouri State Tax Return

How to Amend a Missouri State Tax Return
If you made an error on your original Missouri tax return, file an amended return.

Step 1

Download the Form MO-1040 for the year of the tax return you are amending from the DOR website or obtain one from your local public library. Obtain a copy of Form MO-A if you itemized your deductions.

Step 2

Make a copy of the Form MO-1040 you originally filed, your federal tax return and all other supporting documentation such as your W-2 or 1099.

Step 3

Complete Form MO-1040 and Form MO-A, if applicable, using the correct figures. Complete the “Amended Return” section on page two of Form MO-1040 and add the interest and penalties to the amount you owe.

Step 4

Mail your amended tax return, copies of your original tax return, copies of your federal amended tax return (Form 1040X), and all supporting documentation and a check or money order for any additional amounts owed to:

Missouri Department of Revenue PO Box 329 Jefferson City, MO 65105-0329

If you are due a refund, mail to:

Missouri Department of Revenue P.O. Box 500 Jefferson City, MO 65106-0500