(a) The tax covering the privilege periods included on the initial report is based on the business done by the taxable entity during the period beginning on the taxable entity’s beginning date and:
(1) ending on the last accounting period ending date that is at least 60 days before the original due date of the initial report; or
(2) if there is no such period ending date in Subdivision (1), then ending on the day that is the last day of a calendar month and that is nearest to the end of the taxable entity’s first year of business.
(b) The tax covering the regular annual period, other than a regular annual period included on the initial report, is based on the business done by the taxable entity during the period beginning with the day after the last date upon which taxable margin or net taxable earned surplus on a previous report was based and ending with its last accounting period ending date for federal income tax purposes in the year before the year in which the report is originally due.