(1) An insurance company is subject to the tax imposed by this chapter or by section 476a of the insurance code of 1956, 1956 PA 218, MCL 500.476a, if applicable, whichever is greater.

  (2) The tax year of an insurance company is the calendar year.

  (3) Notwithstanding section 685, an insurance company shall file the annual return required under this part before March 2 after the end of the tax year, and an automatic extension under section 685(3) is not available.

  (4) For the purpose of calculating an estimated payment required by section 681, the greater of the amount of tax imposed on an insurance company under this chapter or under section 476a of the insurance code of 1956, 1956 PA 218, MCL 500.476a, shall be considered the insurance company’s tax liability for the immediately preceding tax year.

  (5) The requirements of section 28(1)(f) of 1941 PA 122, MCL 205.28, that prohibit an employee or authorized representative of, a former employee or authorized representative of, or anyone connected with the department from divulging any facts or information obtained in connection with the administration of a tax, do not apply to disclosure of a tax return required by this section.