Purpose of the tax change would be to fairly distribute tax burden, simplify the tax code, and to eliminate manipulation of existing tax codes and tax returns.
When products and services are purchased they would be taxed.
This system has been used on the state level in the form of "sales tax".
This system has been successful in every state that uses the method.
A federal tax rate could be established by picking a test city where a preliminary tax rate would be implemented after mathematical studies are conducted to target the proper rate.
I surmise the rate would be between 15-20 percent...
A flat tax includes foreign and national expenditures, not to mention those people with lots of money and those folks without.
Nobody would be precluded from paying taxes at a fair rate.