Until or unless everything is centralized and cash ceases to exist, I don't know how they'd really do it. In South Korea do waiters live on tips? Because in the US, almost all money made in the restaurant service industry comes from unrecorded cash tips; the actual wages are extremely low. The restaurant will attempt to estimate their workers tips and cover the taxes out of the fixed wages, but... this doesn't even get into all the other cash industries like stripping or moonlighting as a dominatrix. The US's tax attitude seems to be: You're on your honor, and most of the time we won't catch you, but not even Jesus can help if we do.