(1) An individual need not file a declaration of estimated tax required by ORS 316.563 (1), if:
(a) The estimated gross income of the individual from farming or fishing, including oyster farming, for the taxable year is at least two-thirds of the total estimated gross income from all sources for the taxable year; or
(b) The gross income of the individual from farming or fishing, including oyster farming, shown on the return of the individual in the preceding taxable year is at least two-thirds of the total gross income from all sources shown on such return.
(2) For purposes of computing gross income under this section, an individual who is a stockholder of one or more electing small business corporations for federal income tax purposes shall consider his or her share of the gross income of the electing small business corporation as his or her individual income. The electing small business corporation gross income shall be classed as farming, fishing, nonfarming or nonfishing as the case may be in carrying out the provisions of this section.