15-30-142. Returns and payment of tax -- penalty and interest -- refunds -- credits. (1) Each single individual and each married individual not filing a joint return with a spouse and having a gross income for the tax year of more than $1,500, as adjusted under the provisions of subsection (7), and married individuals not filing separate returns and having a combined gross income for the tax year of more than $3,000, as adjusted under the provisions of subsection (7), are liable for a return to be filed on forms and according to rules that the department may prescribe. The gross income amounts referred to in the preceding sentence must be increased by $800, as adjusted under the provisions of 15-30-112(6), for each additional personal exemption allowance that the taxpayer is entitled to claim for the taxpayer and the taxpayer's spouse under 15-30-112(3) and (4). A nonresident shall file a return if the taxpayer's gross income for the tax year derived from sources within Montana exceeds the amount of the personal exemption that the taxpayer is entitled to claim for the taxpayer and the taxpayer's spouse under the provisions of 15-30-112(2) through (4).
     (2) In accordance with instructions set forth by the department, each taxpayer who is married and living with husband or wife and is required to file a return may, at the taxpayer's option, file a joint return with husband or wife even though one of the spouses has neither gross income nor deductions. If a joint return is made, the tax must be computed on the aggregate taxable income and the liability with respect to the tax is joint and several. If a joint return has been filed for a tax year, the spouses may not file separate returns after the time for filing the return of either has expired unless the department consents.
     (3) If a taxpayer is unable to make the taxpayer's own return, the return must be made by an authorized agent or by a guardian or other person charged with the care of the person or property of the taxpayer.
     (4) All taxpayers, including but not limited to those subject to the provisions of 15-30-202 and 15-30-241, shall compute the amount of income tax payable and shall, at the time of filing the return required by this chapter, pay to the department any balance of income tax remaining unpaid after crediting the amount withheld, as provided by 15-30-202, and any payment made by reason of an estimated tax return provided for in 15-30-241. However, the tax computed must be greater by $1 than the amount withheld and paid by estimated return as provided in this chapter. If the amount of tax withheld and the payment of estimated tax exceed by more than $1 the amount of income tax as computed, the taxpayer is entitled to a refund of the excess.
     (5) As soon as practicable after the return is filed, the department shall examine and verify the tax.
     (6) If the amount of tax as verified is greater than the amount paid, the excess must be paid by the taxpayer to the department within 60 days after notice of the amount of the tax as computed, with interest added at the rate of 9% a year or fraction of a year on the additional tax. In that case, there may not be a penalty because of the understatement if the deficiency is paid within 60 days after the first notice of the amount is mailed to the taxpayer.
     (7) By November 1 of each year, the department shall multiply the minimum amount of gross income necessitating the filing of a return by the inflation factor for the tax year. These adjusted amounts are effective for that tax year, and persons who have gross incomes less than these adjusted amounts are not required to file a return.
     (8) Individual income tax forms distributed by the department for each tax year must contain instructions and tables based on the adjusted base year structure for that tax year.

     History: En. Sec. 14, Ch. 181, L. 1933; re-en. Sec. 2295.14, R.C.M. 1935; amd. Sec. 1, Ch. 34, L. 1949; amd. Sec. 8, Ch. 260, L. 1955; amd. Sec. 2, Ch. 227, L. 1957; amd. Sec. 5, Ch. 253, L. 1959; amd. Sec. 1, Ch. 201, L. 1963; amd. Sec. 1, Ch. 347, L. 1969; amd. Sec. 1, Ch. 450, L. 1973; amd. Sec. 171, Ch. 516, L. 1973; amd. Sec. 1, Ch. 159, L. 1977; R.C.M. 1947, 84-4914(part); amd. Sec. 12, Ch. 698, L. 1979; amd. Secs. 5, 6, I.M. No. 86, approved Nov. 4, 1980; amd. Sec. 1, Ch. 4, L. 1981; amd. Sec. 2, Ch. 477, L. 1981; amd. Sec. 3, Ch. 548, L. 1981; amd. Sec. 8, Ch. 14, Sp. L. July 1992; amd. Sec. 12, Ch. 634, L. 1993; amd. Sec. 2, Ch. 435, L. 1995.