You will have to mail your Colorado state return forms to:
If you are submitting the form with a check or payment:
Colorado Department of Revenue
Denver, CO 80261-0006
If you are submitting the form without a check or payment:
Colorado Department of Revenue
Denver, CO 80261-0005
When filing a paper return, all W-2s and/or 1099s that show Colorado income tax withholding must be attached to the front of the form where indicated. The Colorado Department of Revenue does not require taxpayers to attach a copy of the federal return to the Colorado return.
