The Data Protection Act 1998 requires everyone (e.g. organisations, sole traders, etc) that process personal information (data controllers) to register with the Information Commissioner’s Office (ICO), unless they are exempt.
On the Information Commissioner’s website is a registration self assessment which takes about 5 minutes to complete. By going through the questions you will be able to decide if you – as an individual or on behalf of your business or organisation – need to register with the ICO.
Start the registration self assessment. (this is a link to the ICO website)