I'm surprised that nobody mentioned tax brackets.
I laughed my ass off when my racist uncle smugly explained that he turned down a raise, because that would put him in an upper tax rate and cost him more money than the raise was worth.
Tried to explain how income tax works. Didn't go through that thick skull of his.
Ah sorry, I live in a country where we don't require every single citizen to hire an accountant to file their taxes.
My condolences.