Code of Colorado Regulations 1 CCR 201-2: Income Tax (Taxation Division)

The filing of a return by a taxpayer is an assessment for the amount of the tax due thereon together with the penalty and interest shown to be due thereon. The mailing of a notice with a demand for payment of any tax, penalty and interest imposed under the Act or for payment of any deficiency is an assessment. A deficiency arises from the failure of a taxpayer to pay the full amount of the tax due or to make a proper return or because an additional tax is found to be due. A notice to a taxpayer that the executive director believes a deficiency exists is not an assessment. (See 39-21-103, C.R.S. 1973) Any assessment under this Act is a debt due from the taxpayer to the state of Colorado for the amount shown (a) in the return as of the due date of that return or, (b) in a notice of final determination accompanied by a demand for payment which is not paid or against which an appeal is not filed within 30 days after date of mailing. Any notice and demand under the Act mailed to the last known address of the taxpayer shall be prima facie evidence of service of such notice and demand.