A flat tax is fair because it would prevent politicians from hiding tax breaks in the tax code. Flat tax is claimed unfair because the rich and poor pay the same percentage, in most countries it is 14-20%. A 15% tax will affect a poor person more than a wealthy person. For this reason our tax code is staggered. The difference is that to help the poor, you now have to pass legislation, which means someone has to put their signature on a bill in which the government has to spend money. If you do it with the tax code, no one can be held accountable.