 The Constitution, however, does not require an income tax, it only allows one.Separate income taxes enforced by individual states would be unaffected by the federal repeal.Since passing the FairTax would only require a simple majority in each house of the United States Congress and the signature of the President, and enactment of a constitutional amendment must be approved by two thirds of each house of Congress, and three quarters of the individual U.S. states, it is possible that passage of the FairTax bill would simply add another taxation system.