I don't see how this is easily solvable. Whatever tipping cap you introduce will get maxed out, even in situations where tipping didn't use to be the norm. Zero

I don't see how this is easily solvable. Whatever tipping cap you introduce will get maxed out, even in situations where tipping didn't use to be the norm. Zero tax is a lot less than any finite tax. Also, even if you close the loophole in the law, enforcing it is a nightmare, since the tax office needs to process every single tip now, otherwise someone could slip a few thousand dollar tips through the gaps in enforcement.