Amending Returns

Amended returns replace the original tax return. Therefore, it is imperative to attach/include all schedules and supporting documents with the 104X even when you are not changing the amount in a particular schedule. If the original return included a 104CR schedule, the 104CR must be included with the amended return EVEN WHEN THE 104CR INFORMATION OR DATA DID NOT CHANGE on the amended return. All documentation must be included with the amended return, otherwise processing will be delayed or credit, subtraction or refund claims may be denied. See the Web page Correcting a Return.   

  • The 104X and schedules must be completed and submitted together, whether this is done in Revenue Online or on paper. If a paper 104X is filed, do not re-submit the original 104 form. This will only complicate and delay return processing.
  • Make sure you use the appropriate 104X version for the year you are amending because the 104X is year-specific (for example, use a 2010 Form 104X for an amended 2010 return).
  • Individual income tax returns from 2009 and forward may be amended electronically through Revenue Online (
  • When changing the Colorado return because the IRS made changes to the federal return, you must file Form 104X within 30 days of being notified by the IRS. When the IRS makes changes to federal taxable income, the Colorado return MUST be amended, even if there is no net change to the Colorado tax liability.
  • For more tips on how to amend an individual income tax return and information about how to avoid other common filing income tax filing errors, see the Web page How to Reduce Filing Errors on Income Tax Returns.