C.R.S. § 39-11-115: To whom tax lien shall be sold.

(1) When the taxes levied for the preceding year or years on any properties remain unpaid, the tax liens on such properties offered at tax lien sale at the times provided by law must be sold to the persons who pay therefor the taxes, delinquent interest, and fees then due thereon or who further pay the largest amount in excess of said taxes, delinquent interest, and fees. The excess amount must be credited to the county general fund. Each tax lien must be sold for an entire piece of property. The taxes, delinquent interest, and fees draw interest at the rates fixed by law, and, when the tax liens on any properties are bid in by the county, city, town, or city and county, the amount for which they are bid in draw interest at the same rates. Property for which a tax lien is sold may be redeemed in the manner provided by law.

(2) In order that the tax lien sale may be conducted in an efficient and equitable manner, the treasurer is hereby granted broad powers to set bidding rules governing the tax lien sale. Such powers include, but are not limited to, the following:

(a) Recognition of buyers in numerical sequence, in rotation, or in the order in which bids are made;

(b) Determining the order in which tax liens are sold, without regard to the order in which they appear in the published notice of sale;

(c) Setting minimum bid increases; and

(d) Setting a minimum total of taxes, delinquent interest, and costs below which competitive bids will not be accepted.

(3) The treasurer may combine and sell as a unit parcels which are contiguous or are contained within one subdivision.

(4) The treasurer shall announce bidding rules at the beginning of the tax lien sale, and the rules announced apply to all bidders throughout the sale. If the tax lien sale is conducted by means of the internet or other electronic medium, the treasurer shall post the internet bidding rules on the medium for at least two weeks before the date of sale. The internet bidding rules posted apply to all bidders throughout the sale.