So many people have supported a national flat tax. In the global currency reset circle, a flat tax of 17% had been predicted to start January 1st, 2020. But the flat tax is no more Constitutional than the graduated income tax. The Constitution for the United States or America forbids any direct tax from the federal government without regard to apportionment.
As we see in Article I, Section 2, Clause 3
Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.
to distribute or allocate proportionally; divide and assign according to some rule of proportional distribution:
This being the case, the federal government could charge $1,000.00 per head in each of the states, but the second that any one people is requried to pay more or less that any other one people, the tax is no longer apportioned and is not a lawful tax in compliance with The Constitution for the United States of America.