Colorado Revised Statutes Title 32. Special Districts § 32-11-548. Bid requirements

(a) Be in writing and be sealed; and

(b) Except any bid of the state or any board or department thereof, if one is received, be accompanied by a deposit of an amount of at least two percent of the principal amount of the securities, either in cash, or by cashier's check or treasurer's check of, or by certified check drawn on, a solvent commercial bank in the United States, which deposit shall be returned if the bid is not accepted.