The rate of the tax imposed by and computed under this chapter is:

1. (1) Six and six-tenths percent of the first $1 million of taxable income, or fraction thereof; and
2. (2) Seven and six-tenths percent of any amount of taxable income in excess of $1 million.

[1975 c.368 §2; 1983 c.162 §5; 1987 c.293 §34a; 2009 c.745 §§5,7,9; 2013 s.s. c.5 §1]