Pay Tax or not to pay Tax, that is the question...lol

We are starting out in the business very soon, have received the pitch, got a trailer in mind, food hygiene courses completed and the money available (luckily) to start up without to much of an initial risk.

However the question is, as long as we pay our NI contributions annually(our choice) are we breaking the law if we set up and sell our food without either filling out a self assessment tax form, or register as a business etc.

As im sure all of us would prefer not to declare our earnings but how would they find out if we just set up and sell?

Possibly a very bone question and apologies if i sound a bit stupid, but, have you ever been on the Government Tax website....you need to be a rocket scientist to understand it.

Thanks in advance

Leigh