Protest Rights

You received a Notice of Deficiency or Rejection of Refund Claim from the Colorado Department of Revenue (CDOR). Now what should you do? 

1. Review

Review the notice and compare it to your corresponding tax return. You should be able to see what changes the department made.

2. Research

Research the change to see if it is accurate. Our FYI publications can help you more fully understand the nature of the tax or credit that was modified. The instructions and forms that correspond to your tax return are other good sources of information.
Types of Business Tax Billing Notices
  • Adjustments the Department Makes to Your Return. Additionally, the department issues bills for adjustments or corrections it makes that result in additional tax due.
  • Missed the Filing Deadline. The department issues notices for penalty and interest when a return for any physical site (location) is not filed and paid on time. Both the return and the payment must be received by the due date of the return to be considered timely.
  • No Sales Tax Return Filed. The department also issues notices when it does not receive a sales tax return for any physical site (location). Licensed retailers are required to file a sales tax return for every period during which they maintain an active sales tax account. This requirement applies even if the retailer makes no sales and collects no tax during a given period. If no return is received, the department will assess estimated tax, penalty and interest.

3. Respond or Remit


The notice you received should inform you what documentation the department requires you to send. Be sure to enclose a copy of your notice with your response, and a cover letter that includes the following. You may also submit the protest through Revenue Online, File a Protest.

  • Name and address of taxpayer
  • Source Code (code listed in the upper-right of the letter)
  • The taxable period(s) involved
  • The amount(s) and kind(s) of tax in dispute
  • An itemized schedule of the findings with which the taxpayer does not agree
  • A statement summarizing the reasons the taxpayer believes the tax is not due 
  • Affirmative or negative determination of taxpayer to use brief in lieu of hearing as provided in §39-21-103(7), C.R.S. You have the right to a hearing with the Executive Director, or you may file a written brief in lieu of the hearing. However, you have only 30 days from the mailing date of the notice to request a hearing or to file your written brief. By law this requirement cannot be extended or negotiated by the department.
  • Taxpayer signature. Signature can be the named individual taxpayer, general partner of a partnership, officer of a named corporation, or an individual authorized by such proper person's power of attorney. If the written brief is prepared by counsel, counsel must also sign.
  • The department will review your case in the order in which it was received. Depending on the department's caseload and nature of your case, it may take up to six months for a response to your protest.

- OR -


Send CDOR your payment if you agree with the changes. Several payment options are available.

  • Make a Payment on Your Account Electronically, through Revenue Online. Select Make a Payment. (not available for Cigarette, Tobacco, Liquor, Fuel or IFTA)
  • By Mail: Use the payment voucher that came with the notice or see the instructions and forms page and select the appropriate tax type that applies to the notice.
  • Request a Payment Plan (Income Tax Only): Set up a User ID and Password in Revenue Online if you have not already done so. Then you may request a payment plan online for income tax. Or you may call the Collections Section, 303-205-8291.