Mont. Code Ann. § 18-1-201

18-1-201 . Requirement for bidder's security. (1) A "public authority" or "obligee" includes:

(a) the state of Montana or any department (including the department of administration, unless otherwise authorized by express provision of law), institution, board, commission, agency, authority or subordinate jurisdiction thereof;

(b) any county or other political subdivision of this state;

(c) any municipal corporation or authorized subdivision thereof; or

(d) school districts, irrigation districts, or other public authority organized under the laws of the state of Montana.

(2) Except as provided in 18-4-312 , in all cases where a public authority or obligee is authorized by law to solicit bids, tenders, or proposals for public works, improvements, or undertakings of any kind or for the purchase of commodities, goods, or property or for the procurement of technical or special services on a bid basis (exclusive of services on the basis of salaries or wages) or for the sale and purchase of bonds, debentures, notes, or any other forms of indebtedness of any such public authority, the respective executive, administrative, or other officers of and acting for such public authority shall require, as a condition precedent to considering any such bids, as evidence of good faith on the part of the bidder, and as indemnity for the benefit of such public authority against the failure or refusal of any bidder to enter into any written contract that may be awarded upon and following acceptance of bid or as a condition precedent to consummating any sale and purchase of any forms of indebtedness, that any bid shall contain a written covenant of indemnity conditioned as herein prescribed and that the bid shall be accompanied by bid security of the nature herein specified for the performance of such covenant.