States that have a personal flat income tax rate: Aug, Sat, 2010 admin Taxes 1 minute Read 1.Colorado-4.63% 2.Massachusetts-5.3% 3.Indiana-3.4% 4.Illinois- 3% 5.Utah-5% 6.Pennsylvania-3.07% 7.Michigan-4.35% NB- this is not the same as sales tax.