With this system the poor will pay less and the rich will pay more, because the poor will spend less and the rich will spend more.
By replacing income tax with sales tax anyone that is in the country and spends any amount of money will be paying taxes, eliminating the issue of immigrants avoiding taxes, as well as taking away many of the loopholes the rich use in todays current tax system. This allows us to generate more tax revenue for the country.
People will have more motivation to work overtime. As of now, so many taxes are taken out of a check with ample hours of overtime that many dont see the benefit of working extra. If people saw every dollar they worked for on their checks they would work more, spend more, and would thus contribute more in taxes.