15-30-2113. (Temporary) Determination of marital status. For purposes of this chapter:

(1) the determination of whether an individual is married must be made as of the close of the individual's tax year, except that if the individual's spouse dies during the individual's tax year, the determination must be made as of the time of death; and

(2) an individual legally separated from the individual's spouse under a decree of divorce or of separate maintenance may not be considered as married.

15-30-2113. (Effective January 1, 2024) Determination of status -- effect of status elections. For purposes of this chapter:

(1) the determination of marital status, dependent status, status as an association, partnership, or individual, and any other status must be made as provided in the Internal Revenue Code;

(2) the status that a taxpayer claims or elects in a federal income tax return with respect to the taxpayer or another individual or that the taxpayer or other individual is determined to have for federal income tax purposes conclusively determines the status of that individual; and

(3) a joint Montana individual income tax return must be filed for any tax year for which a joint federal income tax return is filed unless one of the individuals is a nonresident for any part of the tax year.