Colorado Form DR 1778 E-Filer Attachment: Upload or Mail Options

Colorado Form DR 1778 is the cover sheet you mail to the Department of Revenue when your electronically filed state income tax return needs supporting documents, such as credit certificates or receipts, that your tax software could not transmit with the return. Before you fill it out, check two things: whether your tax software can attach PDFs directly to the e-filed return, and whether you can upload the documents through Revenue Online instead. If either works, you can skip DR 1778 entirely. The Department recommends the Revenue Online upload because it reaches your account by the next business day, while mailed paperwork can add up to six weeks to processing.1Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form

When You Actually Need This Form

You need to send supporting documentation separately whenever your Colorado return claims a credit or subtraction that requires proof of eligibility.2Colorado Department of Revenue – Taxation. E-Filer Attachments Common examples are Enterprise Zone contribution certificates, conservation easement credit documentation, the DR 0617 for an innovative motor vehicle credit, supplemental schedules your software could not include, and purchase or lease receipts tied to a claimed credit.

DR 1778 itself is only required if you are mailing paper. If your tax software supports PDF attachments to the e-filed return, use that. If it doesn’t, upload through Revenue Online. The paper form is the fallback when neither of those is available to you.1Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form

One boundary worth flagging: none of these submission methods is the right channel for responding to a letter, bill, or notice the Department has already sent you. More on that below.

Faster Option: Upload Through Revenue Online

Revenue Online uploads reach the Department immediately and are linked to your tax account by the next business day.2Colorado Department of Revenue – Taxation. E-Filer Attachments You do not need to log in or create an account to upload attachments for an individual income tax return, and you do not need DR 1778 at all when you use this method.1Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form

From the Revenue Online home page (without logging in), find the “File a Return or PTC Form” box and select “Submit an e-Filer Attachment.” The prompts walk you through taxpayer information, filing period, tax type, document type, and the file upload itself. At the end you’ll get a confirmation number.

Save that confirmation number. Because you didn’t log in, the submission will not appear in any account history, and the confirmation number is your only record that the upload happened.2Colorado Department of Revenue – Taxation. E-Filer Attachments

If You’re Mailing: Filling Out DR 1778

Download the version of DR 1778 that matches your filing year from the Department of Revenue’s website. Using an older form can cause a mismatch with the current year’s processing.

The form is short. You will fill in:

  • Taxpayer’s last name or business name, written exactly as it appeared on the e-filed return.
  • SSN, ITIN, or FEIN. If you filed jointly, add your spouse’s SSN or ITIN.3Colorado Department of Revenue. DR 1778 Colorado E-Filer Attachment Form
  • Your current mailing address.
  • Signature and date.

The identification numbers are the piece that matters most. If the SSN, ITIN, or FEIN on the form doesn’t match what the Department has from your electronic return, the paper documents may never get linked to your account, and the credit tied to them can be denied while you untangle the mismatch.

Where to Mail It

Send the completed DR 1778 and all supporting documents to:

Colorado Department of Revenue
Denver, CO 80261-00061Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form

Use a trackable mailing method. If a credit is later denied and the question becomes whether you submitted on time, delivery confirmation is what resolves it.

How Long Each Method Takes

Revenue Online uploads post to your tax account by the next business day, and the Department can begin reviewing the return and the supporting documents from that point.2Colorado Department of Revenue – Taxation. E-Filer Attachments Mailed submissions with DR 1778 can add up to six weeks to overall return processing, because the paperwork has to be received, scanned, and manually matched to your electronic return.1Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form If the Department needs anything beyond what you sent, it will contact you by U.S. mail.

If Documents Are Missing or a Credit Gets Denied

Failure to submit required documentation on time results in denial of the related credit.1Colorado Department of Revenue – Taxation. DR 1778 – E-Filer Attachment Form If you realize after e-filing that you forgot the attachments and haven’t yet received a notice, upload them through Revenue Online or mail them with DR 1778 as soon as possible. The earlier they arrive, the less likely your return stalls in review.

If the Department has already issued a Notice of Deficiency or Rejection of Refund Claim, follow the protest rights and procedures printed on the notice itself.4Department of Revenue – Taxation. Refund This is where people most often go wrong: they receive a denial letter, try to resubmit the missing documents through the e-Filer Attachment portal, and the Department never connects the upload to the open notice. The attachment portal is for documents supporting a return, not for responding to correspondence. To respond to a notice, log in to Revenue Online and select “Protest a Notice or Letter” under “Additional Services.”2Colorado Department of Revenue – Taxation. E-Filer Attachments