It’s actually more complicated than you think. Here’s the starting point of the complexity. When do you tax someone’s investment earnings? When do you tax someone’s business? When do you tax someone’s income from abroad? If they live part of their life abroad, how much of their income does your country tax? … If you think the above have simple answers, then you don’t understand the actual situations that people are living.

It’s great to say that a flat tax is simple and it will work but in reality actually it’s not simple at all because there are always ways to gain the system and you have to find those and keep working on fixing them.