(a) Said tax shall be levied, collected and paid with respect to the salaries, wages, commissions and other compensation earned on and after January 1, 1973 and with respect to the net profits of business, professions or other activities earned on and after January 1, 1973. Provided, however, that where the fiscal year of the business, profession or other activity differs from the calendar year, the tax shall be applied to that part of the net profits for the fiscal year as shall be earned on and after January 1, 1973, to the close of the taxpayer's fiscal year. Thereafter, the taxpayer shall report on its fiscal year basis.
(b) Where the fiscal year of a business, profession or other activity is other than a calendar year, in computing initial tax, the profits of such taxpayer shall be determined by dividing the annual profits by twelve (12) and multiplying the quotient by the number of months within the period commencing January 1, 1973, and ending at the conclusion of said fiscal year.