The biggest difference moving to a flat tax system can make is that you can shift income tax collection from the payee to the payer. Under a progressive system

The biggest difference moving to a flat tax system can make is that you can shift income tax collection from the payee to the payer. Under a progressive system, Company A paying you $10,000 and Company B paying you $10,000 results in a different tax rate so neither company knows how much tax you owe. Under flat tax, Company A can just take $1500 out of your earnings before it gets to you, regardless of any arrangements you have with other payers. Since there are far fewer companies than employees, this makes tax enforcement significantly easier and evasion much less likely. Ordinary citizens now no longer have to deal with the IRS and tax is handled transparently. Every flat tax proposal also tends to come with a negative income tax component to make up for the regressivity. The NIT essentially becomes a basic income like social safety net to make up for the loss of progressivity. And since it involves the govt giving you money rather than you giving the govt money, compliance will naturally be much higher.