Related Information

Question: What must I do if I receive an income tax Math Audit letter?
Receipt of a math audit letter indicates that your income tax return was filed without required documentation or that there were incorrect calculations on the return. The math audit letter lists the adjustments made to the return.

If you receive a math audit letter review it carefully to find out what changes or adjustments were made to your return. If the letter is a result of missing documentation you may attach the documentation to your account through Revenue Online. If you believe you received the math audit letter in error, you can also file a Protest electronically through our Revenue Online service.

Some of the most common reasons why a taxpayer may receive a math audit letter from the Colorado Department of Revenue are:

  • Missing attachments such as W-2s, Form 104CR, Form 104PN or other required schedules.
  • Return was filled out incorrectly, resulting in a calculation or math error (usually a paper return).
  • Incorrect amount of a specific credit was claimed -- either by overclaiming or underclaiming a credit amount.

If computer access to Revenue Online is not available, you can mail a copy of the letter, a copy of the return, supporting documents and a letter stating why you believe the letter was issued in error. Math Audit protest letters should be sent to:

Colorado Department of Revenue
Income Tax Accounting Section
1375 Sherman St. Rm. 238
Denver, CO 80261

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