DOR Taxation web site

Amending Income Tax Returns

Posted: July 13, 2010
Tips for Filing Colorado income tax amended returns

When filing a Colorado amended return for individual income tax, please follow these tips to avoid processing delays:

  • ALWAYS use the form that matches the year you are amending. For example, if you are amending a 2009 return, use the 2009 104X form. If you use a form for another tax year, the lines from one tax year to another are different. Using an incorrect year form will delay processing and cause errors.
  • The 104X file on our Web site includes the 104CR and 104PN. Even when there is no change to the 104CR credit schedule or the 104PN part-year/nonresident form, those forms must be completed again (or you must include copies submitted with the original return). Also attach other schedules or credit certifications to the amended return even if copies were attached to original return. Failure to attach these documents will result in delays and errors.
  • The 104X form should be the first form we see in any amended packet you send to us. Place the 104CR, 104PN and other supporting documents behind the 104X.
  • The 104X form is now different than prior years. All 104X forms from 2005 through present have been updated for use in the Colorado Department of Revenue’s new tax accounting system. This means there is only one column for the corrected information (not three columns as in prior years). These forms have been available on our Web site since October 2009.
  • DO NOT include a copy of the 104 (original) return with the 104X.

Individual income tax amended returns (104X) are available online.

For corporations, fiduciaries and partnerships, the same rules apply about using the form that matches the year you are amending and placing the amended return on the top of the packet you submit.

Corporation amended returns (112X) are also now one column.

For fiduciary and partnership amended returns, use the 105 or 106 form as the amended return.

  • Be sure to CLEARLY MARK the Amended Return checkbox at the top of these forms.
  • The place to indicate “amended return” is at the top of the 105 and 106 forms and it reads: “Check here if this is an amended return for calendar year or other tax year.”
  • To ensure the 105 and 106 returns will be noticed in our processing pipeline as amended when we receive them, write AMENDED RETURN in red across the top to draw attention to the return.