Colo. Rev. Stat. § 39-5-117
Whenever any improvements are destroyed or demolished subsequent to the assessment date in any year, it is the duty of the owner thereof or the owner's agent to promptly notify the assessor of such destruction or demolition and the date upon which the same occurred. In all such cases, such improvements shall be valued by the assessor at the proportion of its valuation for the full calendar year that the period of time in such year prior to its destruction or demolition bears to the full calendar year. Failure of the owner thereof or of the owner's agent to so notify the assessor prior to the date taxes are levied shall be considered a waiver, and no proportionate valuation by the assessor shall then be required.
C.R.S. § 39-5-117
(1) For the assessment date, see § 39-1-105. (2) For the legislative declaration contained in the 1996 act amending this section, see section 1 of chapter 16, Session Laws of Colorado 1996.