Couldn't really find a suitable forum for this...

I'm 17 years old, and at school/sixth form studying for A levels.

I'm into web design as a hobby, but do paid work, and have a website advertising web-design.

Should I have registered as a business or gone through any legal procedures? Someone suggested I only needed to if I was actually selling goods, or if I was doing it as a full time job, but I'm not sure... I can't find much info about this anywhere, so I'm hoping someoen out here can help.