You have to register as self employed by telephone or form. Dont forget that you will pay NI at a standard �2.20 per week and then class 4 NI is payable at 8% on profit at the end of the tax year with your tax bill. if you registered now you would receive a tax return April 08 submit by end of oct 08 for HMRC to calculate tax for you. if you file online you have until the end of jan 09 to file and pay your bill. of course if you are doing this as a second job then if all your `allowances will probably be used on that so any earnings on SE would be at 22% now and 20% in 08-09