(1) The director of revenue or any person authorized in writing by the director is authorized to enter into an agreement with any taxpayer relating to the liability of the taxpayer in respect to the tax imposed by this chapter for any taxable period.
(2) Any agreement is final and conclusive, and except upon a showing of fraud or malfeasance or misrepresentation of a material fact:
(a) the case may not be reopened as to matters agreed upon or the agreement modified by any officer, employee, or agent of this state; and
(b) in any suit, action, or proceeding under the agreement or any determination, assessment, collection, payment, abatement, refund, or credit made in accordance with the agreement, the agreement may not be annulled, modified, set aside, or disregarded.