Instituting a national sales tax and eliminating income tax would remove an archaic and convoluted system that can be easily circumvented.
A national sales tax would ensure that undocumented residents, people with undocumented income and criminals all pay into the system. It would close existing income tax loopholes that have a tendency to be abused.
A single percentage should be used for all income classes as the revenue would increase or decrease based on the amount a person spends. Unprepared food items should be untaxed just as they are in most states' sales tax implementations.