There are three aspects to choosing a domain name:
Having decided on your domain name, you then need to check whether it is available or whether it has been registered already by another user. This is done by using the WHOIS service, an online search facility that provides details of domain name registrations in a matter of seconds.
Bear in mind that when you register a domain name, you are agreeing to abide by our terms and conditions, which is separate to the contract you will have with your registration agent (ISP) - explained more here. The terms and conditions require that you declare that the registration does not infringe the rights of others - for example, their trade mark rights. If a third party thinks that your domain registration takes unfair advantage of their rights they can sue you or take the dispute to our Dispute Resolution Service (DRS) which deals with these disputes quickly and cheaply.
The duty not to interfere with third party rights applies to individuals and companies. Although a company may have traded with a similar name for many years - and, in the case of sole traders and partnerships, with exactly the same name - only one can use it as a domain name.
Our case law section gives some information about how the courts deal with this, but if you want more information you should seek independent legal advice. If you want more information about registered trade marks, see the Patent Office or the Institute of Trade Mark Attorneys. In the DRS 'rights' has a specific meaning, explained here.