It isn't even clear how to make them stop that, per se, because in general that's a desirable characteristic of the system. You can't use the tax system to nudge people or do anything progressive beyond the most basic and clumsy income-bucket based categorization if you can't set up incentives and expect people to "optimize" to them.
Say you make 15k a year, your tax rate is zero, 16k, it's perhaps 1%, etc. etc. until you get to the big dogs who net millions a year, far more than they could reasonably spend on their own living expenses and well being, then you tax them 90%.
Or maybe you can add tax on every purchase if you have a certain level of wealth. Someone who is broke might reserve a $2 coke for a special treat if they only made $50 that day, but if you made 50k that day it's still a $2 coke and not a $2000 coke. Replace coke with house, car, tuition, medical bills, anything you want.
In the current system you can hide your income in a company and pay yourself remarkably little on paper, so I say tax those companies heavily as well. If money is fungible, taxes should be too and it shouldn't matter if the company makes 1m and you make 100k or if you make 1m and the company makes 100k, the tax burden should be exactly the same as it represents the same movement of 1.1m. The fact that the tax burden isn't the same currently is corrupt and serves the few at the cost of the many.
Any tips? :)