E-Filer Attachments -- Instructions and Forms

Supporting documentation must be submitted to the department in order to prove eligibility for credits claimed on the Colorado Income Tax Return. Using Revenue Online, the department's free, one-stop website for filing taxes, managing accounts and checking refund status, ensures the documentation is immediately available to the department in the taxpayer’s account while reviewing the income tax credit claims. No Login ID is required to upload e-Filer Attachments via Revenue Online into a taxpayer’s income tax account. There are two options for submitting these attachments, depending on filing method.