First off, if you start out from the perspective of setting a fixed amount of income, you run into problems immediately.

Why would you accept all the extra responsibility and work involved in being a department head or a CEO if you get to keep no more of what you earn than you do now.

The idea of making the rich pay more than the poor is very attractive, but there comes a point when you run out of people altruistic enough to accept responsibility without reward.

The reductio ad absurdum argument is that you do away with rich people altogether, losing all your high fliers, and end up with a nation of happy janitors, who can't be bothered to improve their status because "What's in it for them?"

the original ask was for a simple, fiddle proof system, and the only one I can see which will keep people reaching for the top, while not allowing them to dodge taxes when they get there, is the flat rate percentage,or some derivative thereof.

Don T.