DOR Taxation web site

Information and Help Regarding Your Notice

The department sends out many types of notices. You can research why you received the notice and what your options are depending on the notice type. To determine which type of notice was issued to you, please refer to either a Source Code or a letter ID located on your bill. In most cases this information is located on the upper right section of the notice. Can’t find your bill or letter? Visit Revenue Online, Sign Up for account access and view copies of past letters and bills

New: Billing Notices Now Easier to Understand

Source Code
An example of a source code is listed below. The source code will be a mix of letters and numbers which may be separated by a hyphen.


Source: N05-C3

N05 -- The set of characters before the hyphen is the primary identifier to research your notice.
C3 -- If you have any characters after the hyphen, they will narrow down the type of notice to a more specific group. Not all notices will have this identifier.


Letter ID Number
An example of a Letter ID number is:

Letter: L1234567890

There is an L followed by 10 digits.

Please find your source code or letter ID number in the column on the left. Click on the blue wording to open the information for your notice including why you received the notice, how to resolve or protest the notice and who to contact for more information. Click again on the blue wording to close the information. If your source code or notice number is not listed, please call the telephone number listed on your bill.

COL Delinquency Notice
DIS Discovery: Notice
DIS-CG Discovery: Invalid or Unproven Colorado Capital Gain Subtraction
DIS-CN Discovery: No Income Tax Return Reflected On The Departments Records
DIS-CU Discovery: Adjustments Unreported Income
DIS-EN Discovery: No Income Tax Return Reflected On The Departments Records
DIS-EU Discovery: Adjustment Due to IRS Examination Report
DIS-GN Discovery: Miscellaneous
DIS-IN Discovery: No Income Tax Return Reflected On The Departments Records
DIS-IU Discovery: Adjustment State and Federal Comparison
DIS-K1 Discovery: No Income Tax Return Reflected On The Departments Records
DIS-NC Discovery: Notice
DIS-NN Discovery: No Income Tax Return Reflected On The Departments Records
DIS-NK Discovery: No Income Tax Return Reflected On The Departments Records
DIS-NR Discovery: No Income Tax Return Reflected On The Departments Records
DIS-NW Discovery: No Income Tax Return Reflected On The Departments Records
DIS-QR Discovery: Miscellaneous
DIS-VD Discovery: Voluntary Disclosure Assessment
DIS-WI Discovery Section: Wage Withholding discrepancy
FAS Field Audit Section
N05 Tax Account
PRO Tax Account
STA Tax Account
TPB Business Account
TPC Tax Audit and Compliance Section Notice
TPI Individual Income Tax Account
TPP Tax Account