(1) An income tax return with respect to the tax imposed by this chapter shall be made by the following:
(a) Every resident individual:
(A) Who is required to file a federal income tax return for the taxable year; or
(B) Who has gross income greater than the sum of:
(i) The basic standard deduction allowed under ORS 316.695 (1)(c)(B);
(ii) Any additional standard deduction allowed to the taxpayer under ORS 316.695 (7); and
(iii) An amount equal to the income equivalent of one personal exemption credit under ORS 316.085 (3)(b) if unmarried, or equal to the income equivalent of two personal exemption credits under ORS 316.085 (3)(b) if married.
(b) Every nonresident individual who has federal gross income from sources in this state of more than the basic standard deduction allowed under ORS 316.695 (1)(c)(B).
(c) Every resident estate or trust that is required to file a federal income tax return.
(d) Every nonresident estate that has federal gross income of $600 or more for the taxable year from sources within this state.
(e) Every nonresident trust that for the taxable year has from sources within this state any taxable income, or gross income of $600 or more regardless of the amount of taxable income.
(2) Nothing contained in this section shall preclude the Department of Revenue from requiring any individual, estate or trust to file a return when, in the judgment of the department, a return should be filed.
(3) For purposes of this section, the income equivalent of a personal exemption credit under ORS 316.085 (3)(b) shall be determined as follows:
(a) Divide the personal exemption credit amount by the rate applicable to the lowest income bracket under ORS 316.037.
(b) If the resulting quotient is less than the maximum amount of income subject to the rate used in paragraph (a) of this subsection, the quotient is the income equivalent.
(c) If the resulting quotient is more than the maximum amount of income subject to the rate used in paragraph (a) of this subsection:
(A) Multiply the maximum amount of income subject to the rate used in paragraph (a) of this subsection by the rate used in paragraph (a) of this subsection.
(B) Determine the difference between the product calculated under subparagraph (A) of this paragraph and the personal exemption credit amount.
(C) Divide the difference determined in subparagraph (B) of this paragraph by the rate applicable to the income bracket that is the next succeeding the lowest income bracket under ORS 316.037.
(D) Add the quotient determined in subparagraph (C) of this paragraph to the maximum amount of income subject to the rate used in paragraph (a) of this subsection. The sum is the income equivalent.