How to Prepare and File a Colorado Tax Amendment Form


amend Colorado taxes
Colorado
“The Centennial State”

If you need to change or amend an accepted Colorado State Income Tax Return for the current or previous Tax Year, you need to complete Form 104X.  Form 104X is a Form used for the Tax Amendment. You can prepare a 2018 Colorado 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 Colorado Tax Agency, thus you should file a Colorado Amendment within one year.

Function
Description
Prepare only a CO State Return
with a State Only Code: FreeFed19
File a 2018 Colorado Tax Amendment
You cannot eFile a CO Tax Amendment anywhere, except mail it in. However, you can prepare it here on eFile.com.
Only Option: You need to complete, sign Form 104X for the appropriate Tax Year. Attach all schedules and other documents (including original and new, corrected forms and schedules) to your amended return - Print, Mail the Form to CO Tax Department to:
Tax Payment with Amended Return
Colorado Department of Revenue
Denver, CO 80261-0006
No Tax Payment with Amended Return
Colorado Department of Revenue
Denver, CO 80261-0005
CO Tax Amendment Form 104X
This Form can be used to file a: Tax Amendment, Change of Address.
Step 1: Download, Complete Form 104X below for the appropriate Tax Year.  Attach all schedules and other documents (including original and new, corrected forms and schedules) to your amended return. 
Step 2: Sign, Mail Form 104X to one of the addresses listed above
How to correct a rejected Tax Return
If your CO Tax Return was rejected by the CO Tax Agency - not eFile.com - instructions on how to correct a rejected Colorado Tax Return.
For all Tax Years prior to 2018 Prepare, Print, Sign and Mail-In - see addresses above - your Tax Amendment as soon as possible. Attach all schedules and other documents (including original and new, corrected forms and schedules) to your amended return. You will also file an IRS Tax Amendment Form 1040X.
Check Your CO Tax Amendment Status
1. Call the CO Department of Revenue at 303-238-SERV (7378).
2. Contact the CO Department of Revenue
Colorado 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 Colorado 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 Colorado 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 Colorado Tax Income Taxes Deadlines
Colorado Income Tax Penalties
Find out how Colorado 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.