The Department of Revenue is processing 2023 income tax returns. For more information, please read the Department's announcement.


DR 1778 - E-Filer Attachment Form


The Department strongly recommends that you submit these documents using the e-Filer Attachment option on the Revenue Online website, which eliminates the requirement to mail this form. Failure to timely submit required documentation will result in denial of the related credit. Revenue Online E-Filer Attachment provides you with a confirmation number and will be available to the Department immediately. Otherwise, complete this form, package it with your documentation and mail to the Department. Using this form can extend return processing time up to 6 weeks.

Mail to:
Colorado Department of Revenue
Denver, CO 80261-0006