Is it legal to employ anonymous people (or entities I guess) in any country? I guess both parties can pay taxes separately and I assume it has happened for some

Is it legal to employ anonymous people (or entities I guess) in any country? I guess both parties can pay taxes separately and I assume it has happened for some security research, insider info, special consulting, but I don't know if that's actually legal. (It seems to me to go against the common way for governments to regulate workforce.)