I think your question needs some clarification. By “flat rate” do you mean a fixed percentage income tax on individuals, or a fixed percentage consumption tax like a universal sales tax? If it’s an income tax, do you only tax wages or do you also tax interest, dividends, and capital gains? Would any deductions be allowed? Is it only a tax on individuals’ income or do you also tax money earned by legal entities like businesses or investment trusts? If it’s sales tax, do you exempt necessities like food or medicine from the tax?
I think your question needs some clarification. By “flat rate” do you mean a fixed percentage income tax on individuals, or a fixed percentage consumption tax like a universal sales tax? If it’s an income tax, do you only tax wages or do you also tax interest, dividends, and capital gains? Would any deductions be allowed? Is it only a tax on individuals’ income or do you also tax money earned by legal entities like businesses or investment trusts? If it’s sales tax, do you exempt necessities like food or medicine from the tax?