smallbusiness.co.uk: Helping your business think big

 Assuming that you are going to be self-employed and not wanting to run a company, you have to tell the Contributions Agency and the Inland Revenue. But they run a joint registration scheme, so telling one should be enough as they should pass the information to the other. If you think your sales will be above the VAT registration limit (which is £56,000 a year or more) you would also have to tell Customs and Excise.