You may use a paper form to amend your return or you can file a 2009 or later amended return electronically using our Revenue Online service. The return can be filed any time after you have filed your original return, but no later than the statute of limitations expires, which is usually four years from the due date of the original return.

To obtain an amended form, see our Income Tax Forms and select the tax year needed.

The Colorado Department of Revenue now requires that any amended income tax return filed must also have attached to the return any schedule or documentation that pertains to that particular return. This includes attaching the 104PN and 104CR credit schedule to amended returns regardless of what year the filing is for including any income tax credit or subtraction that an amended return is being filed. Supporting documents may be attached online when you file your amended return through Revenue Online.

If all supporting documents are not attached to the amended return, the return may be incorrectly adjusted by the Department of Revenue, which would require a second amended return to be filed to correct the return.