Mont. Code Ann. § 15-1-421 — Payment Of Taxes By Negotiable Instrument

15-1-421 . Payment of taxes by negotiable instrument. The department of revenue is not bound by a special, qualified, conditional, or restrictive endorsement placed on a negotiable instrument by the maker or drawer, tendered to the department for the payment of a tax liability, unless:
(1) the taxpayer and the department have previously entered into a written agreement that specifies the amount of the taxpayer's liability; and
(2) the amount tendered is in accordance with the written agreement.