My favorite flat tax trick is from the 1986 tax reform: 15% and 28% tax brackets, with 28% kicking in when the 7.55% SocSec/Medicare/aid taxes shut off (employer match).
So in the 15% bracket, the next 100 on the paystub was 107.55 employer cash cost, 30.10 in taxes, and a 27.99% rate.
