In theory maybe, in practice, not so much. You'll have a lower sales tax rate across the board than what the working class and middle class currently pay in taxes, so they actually both benefit. There are some families with a negative effective rate and they'll no doubt be affected, but there are ways the government can assist those through applying for a sales tax credit or refund each year when they qualify for it. And you reduce time and money lost prepping taxes for everyone and the federal government ultimately collects more from sales taxes and saves money by reducing the footprint of the IRS substantially. And there would still be the existing programs, i.e. Medicaid, SSI/SSDI etc to assist those who either are unable to work or underemployed.