As used in this chapter, unless the context requires otherwise:
(1) “Department” means the Department of Revenue.
(2) “Director” means the Director of the Department of Revenue.
(3) “Individual” means a natural person, including aliens and minors.
(4) A “nonresident” means an individual who is not a resident of this state.
(5) “Part-year resident” means an individual taxpayer who changes status during a tax year from resident to nonresident or from nonresident to resident.
(6) “Taxable income” means the taxable income as defined in subsection (a) or (b), section 63 of the Internal Revenue Code, with such additions, subtractions and adjustments as are prescribed by this chapter.
(7) “Taxpayer” means any natural person, estate, trust, or beneficiary whose income is in whole or in part subject to the taxes imposed by this chapter, or any employer required by this chapter to withhold personal income taxes from the compensation of employees for remittance to the state.