Oregon Revised Statutes Revenue and Taxation § 316.117

(1) Except as provided under subsection (2) of this section, the proportion for making a proration for nonresident taxpayers of the standard deduction or itemized deductions, the personal exemption credits and any accrued federal or foreign income taxes, or for part-year resident taxpayers of the amount of the tax, between Oregon source income and income from all other sources is the federal adjusted gross income of the taxpayer from Oregon sources divided by the taxpayer's federal adjusted gross income from all sources. If the numerator of the fraction described in this subsection is greater than the denominator, the proportion of 100 percent shall be used in the proration required by this section. As used in this subsection, “federal adjusted gross income” means the federal adjusted gross income of the taxpayer with the additions, subtractions and other modifications to federal taxable income that relate to adjusted gross income for personal income tax purposes.

(2) For part-year resident trusts, the proration made under this section shall be made by reference to the taxable income of the fiduciary.