(1) Except as provided in (3) and (4), a taxpayer who does not claim itemized deductions is allowed the standard deduction.
(2) The standard deduction is 20% of the taxpayer's Montana adjusted gross income subject to minimum and maximum amounts, which are adjusted annually for inflation. The amount of the standard deduction, as adjusted for inflation for recent tax years, can be obtained by accessing past-year downloadable tax forms from the department's internet homepage web site located at: revenue.mt.gov.
(3) The following requirements govern the standard deduction of married taxpayers who do not file a joint return with their spouse:
(a) A married taxpayer filing separately may claim the standard deduction only if his or her spouse does not file a Montana individual income tax return claiming itemized deductions;
(b) As provided in 15-30-2113, MCA, a taxpayer who is legally separated from his or her spouse at the end of the tax year under a decree of divorce, legal separation, or separate maintenance is not considered married for purposes of this rule;
(c) In the event of death of one of the spouses, the restriction described in (3)(a) is applicable with respect to the tax year ending with death and the tax year of the surviving spouse in which the death occurs; and
(d) By filing a separate return claiming a standard deduction, a married taxpayer represents that the taxpayer's spouse did not or will not claim itemized deductions.
(4) A standard deduction may not be claimed for an estate or trust.