C.R.S. § 39-13-107

It is the duty of each assessor to examine at least once each year all documents recorded in his county upon which a documentary fee has been paid and to determine in each case the consideration upon which such fee was computed and paid. He shall compile and maintain in his office a continuing record of all such considerations to assist him in appraising property and determining the actual value thereof as required by the provisions of section 39-1-103 (5).