This experiment evaluates various systems of taxation on the number of real tasks performed by participants and in terms of fiscal income generated to help government in its redistributive goal. The first treatment concerns a proportional system of taxation. The second treatment considers an equivalent progressive income tax system. Finally, participants are submitted sequentially to different flat tax rates. This last treatment evaluates the reaction of participants to fiscal changes. Our results support clearly that a progressive taxation system reduces work effort relative to a single flat tax. The single flat tax system yields more fiscal income. The results also show that individuals are affected by their own tax system and by the other forms of taxation they experienced before