The Government eventually gets all your Income anyway , If you spend it they get it, if not from you then the person you purchase from and so on, so the only way for them not to get it would be for you not to spend it, so what would be the point in you getting income if you didn't spend it. So Income Tax only speeds up the circulation of money to the government by taking it before you earn it instead of after you spend it. What I'm saying is technically Income Tax is not needed for revenue as they will get it from you eventually anyway. Income Tax serves them to get your money sooner rather then later. Make sense?