(1) All corporations filing Montana corporate license or Montana corporate income tax returns for years beginning on or after January 1, 1988, but before December 31, 1988, shall pay an additional four percent (.04) surtax. The surtax is calculated by multiplying the otherwise calculated Montana tax liability by four percent (.04) to arrive at the surtax. The surtax is in addition to the regular tax liability and also applies to the $50 minimum corporation license tax. (2) All corporations filing Montana corporate license or Montana corporate income tax returns for years beginning on or after January 1, 1990, but before January 1, 1991, shall pay an additional five percent (.05) surtax. The surtax is calculated and applies as provided in (1) .