as joe said, if you're going to cheat tax man why wouldn't you cheat your customers? not something you want to start doing as you also run the risk of going too far with it and getting carried away, one cash payment once in a while is ok but if you're going to do it once you might as well twice and three times and it goes on until you get caught. not worth it imo as carpet cleaners get paid well any way, or at least they should be.