And on a more serious note Mr Tax will find you , especially if you are mistress web, mistress PR and the rest, one dancer here in the Northwest discovered this for herself a few years back.
Some of the larger corporate events now offer the fee with tax paid by the client. At least this is what I've found. Recent gig did just that. I got taxed in the normal way as though they were my employer.
And aforementioned dancer got dobbed in to the tax man by someone who saw her dance in the restaurant she was working in....probably a case of sour grapes rather than old fashioned doing it for the good of the Inland Revenue. I seem to recall she eventually found out who it was, because whoever did it made the mistake of confiding in someone else and unfortunately, the BD community in the region is rather small. But just goes to show how dancers do need to keep up with the tax man. If you're not self employed, then don't forget, you still need to declare what you earn... including workshops and classes....just coz you hold down a job that's already paying tax, doesn't mean you can get away with it.