You could do it with a bunch of INDEX-MATCH formulas and pre-calculating base tax per bracket:

  =(income-INDEX(bracket_min,match(income,bracket_min,1)))*
    INDEX(bracket_tax,match(income,bracket_min,1))+
    INDEX(bracket_base_tax,match(income,bracket_min,1))

Clever, but I'm curious why you don't use VLOOKUP?

It's simpler, and Lotus 1-2-3 doesn't have MATCH! :-)

I think something like this would work...

    (income-@VLOOKUP(income,table,1))*@VLOOKUP(income,table,3)+@VLOOKUP(income,table,5)

Habit, mostly: I tend to use VLOOKUP for exact matches and MATCH for relative ones.