It is the intent of the Legislative Assembly, by the adoption of this chapter, insofar as possible, to:
(1) Make the Oregon personal income tax law identical in effect to the provisions of the Internal Revenue Code relating to the measurement of taxable income of individuals, estates and trusts, modified as necessary by the state’s jurisdiction to tax and the revenue needs of the state;
(2) Achieve this result by the application of the various provisions of the Internal Revenue Code relating to the definition of income, exceptions and exclusions therefrom, deductions (business and personal), accounting methods, taxation of trusts, estates and partnerships, basis, depreciation and other pertinent provisions relating to gross income as defined therein, modified as provided in this chapter, resulting in a final amount called “taxable income”; and
(3) Impose a tax on residents of this state measured by taxable income wherever derived and to impose a tax on the income of nonresidents that is ascribable to sources within this state.