Yes you should if you do contract work etc.Even if you are a PAYG earner ( wage ) there can be advatages.And to answer your question the costs are not very high Is it against the law to make money without registering as a business No...Advanatges - Deductions ( Stripper can claim security)Disadvantages - Claiming silly things and getting busted for tax fraudIf you are going into business ( I have an idea etc ) register a comapany for shits and giggles, it will come in handy at some time
I think you have to register when you start making money, i think there is a limit of about 3 thousand pounds before you need to start declaring income. Probably best to register though as it will be more credible e.g. buyers,suppliers etc. and it does not cost a lot to register and can be done quickly.