(1) All returns required by this article shall be made as nearly as practicable in the same form as the corresponding form of income tax return required by the United States.
(2) All returns shall be filed in the office of the executive director on or before the fifteenth day of the fourth month following the close of the taxable year. The executive director may grant a reasonable extension of time for filing returns and for paying the tax under such rules and regulations as he shall prescribe.
(3) Residents who are traveling or temporarily residing outside the United States at the time provided in subsection (2) of this section shall be allowed an automatic extension to and including the fifteenth day of the sixth month following the close of the taxable year in which to file returns.
(4) Notwithstanding subsection (2) of this section, if the time for electronic filing of a federal income tax return pursuant to the internal revenue code is changed to a date later than the date specified in subsection (2) of this section, the executive director may adopt a rule changing the time for electronic filing of a return required by this article to the same date.