how to make an income tax calculator in excel

[Guest]

Try, for an income value in A1 and the 'max' values being
numbers you supply representing the maximum incomes in
their respective brackets...

=if(A1<maxof10pctbracket,income*.1,if
(A1<maxof22pctbracket,income*.22,A1*.4))

This tests for income value being in the 10% bracket
first, and if it's not that then it tests for its being in
the 22% bracket, and if its not that then it assumes its
in the 40% bracket.