system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the corporate tax at a flat rate?

Why can't the tax rate be higher for firms that make more profit and less for firms that make less, making the tax rate progressive for businesses?
gpt
Consider what would happen if we did this: firms would structure themselves to get to the size to obtain a lower tax rate and there would be a massive industry in keeping firms to specific sizes. Basically, it would result in arbitrary economic structures, probably inefficient structures, designed to stay under certain tax levels. 

Then there is the problem of what are we taxing? GAAP net income? What about firms like Amazon which avoid GAAP Net income to avoid taxation?

Picture it like this - economic efficiency is always determined on an after tax basis necessarily, so if we change the way arrive at after tax profits by changing the tax rate, it may be the case that an structure which is technically less economically efficient is *more* efficient because of the way the tax structure is created. Thus, we'd see irrational structures to achieve more after tax profits.