E-Filer Attachments

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.

Income Tax Returns Filed Electronically

Supporting documentation must be submitted to prove eligibility for credits claimed. If your tax software does not support pdf attachments, scanning, saving and uploading an electronic copy of the documentation through Revenue Online is the preferred method of submitting these documents because the copy will be added to the taxpayer’s account and the Department will not need to ask for an additional copy later. No Login ID is required to upload e-Filer Attachments via Revenue Online into a taxpayer’s income tax account. See the instructions for How to Submit an e-Filer Attachment in Revenue Online below. The alternative method is to send the documentation by mail with the form DR 1778: e-Filer Attachment Form. The DR 1778 serves as a kind of "cover letter" for the documents when they arrive at the Department by mail.

Income Tax Returns Filed on Paper

If returns are filed on paper, the documentation to prove eligibility for credits claimed may be attached to the paper income tax return. This method is not recommended because there is the chance the documentation will become separated from the paper return and the Department will need to request it again, which delays processing the income tax filing. Even for returns filed by paper, uploading an electronic copy of the supporting documentation through Revenue Online is still the preferred method of submitting these documents because the copy will be added to the taxpayer’s account and the Department will not need to ask for an additional copy later. No Login ID is required to upload e-Filer Attachments via Revenue Online into a taxpayer’s income tax account. See the instructions for How to Submit an e-Filer Attachment in Revenue Online below. 

How to Submit an e-Filer Attachment in Revenue Online

No Login ID is required to upload e-Filer Attachments via Revenue Online into a taxpayer’s income tax account.
  1. Click on the Submit an e-Filer Attachment link.
  2. Read the instructions and click on the Next button.
  3. Follow the steps to enter the Taxpayer Information, Spouse Information (if applicable), and Mailing Address. Then, click on the OK button.
  4. Enter the Filing Period. Select the Filed Tax Type (corporate, individual or partnership) and Document(s) Submitted. Click on the OK button.
  5. Click on the Attach a File button on the far right side of the screen in the Step 3 section. 
  6. Enter a description of the file to be submitted.
  7. Click the Choose File button to select the electronic file to submit.
  8. Click the Save button to attach the document. The document will be listed in the Attach Documents section. To remove a file, click on Remove on the far right.
  9. Click on the Attach a File button on the far right side of the screen to upload any additional attachments. 
  10. When all attachments have been added and appear in the list for Step 3, click on the Submit button. A pop-up box will appear to confirm that the attachment(s) should be submitted. After reviewing all the information to ensure it is correct, click on the OK button. 
  11. The following confirmation message will display on the screen: Your request for e-Filer Attachments has been sent to the Department of Revenue. A confirmation number will also display. Copy or print this screen to keep with tax records.
  12. The document(s) will be added to the taxpayer’s account (internal DOR system) the next business day. Because no Login ID is required to submit an e-Filer Attachment, the request will not be shown in the taxpayer’s Revenue Online account when they log into the account.