This answer will explain what a Confirmation of Registration letter is, which domain names receive them, and what to do when you're issued with one. Confirmation of Registration letters are sometimes referred to as 'domain name certificates' or 'registration certificates'.
A Confirmation of Registration letter confirms that a domain has been successfully registered. It is issued by Nominet (the Internet Registry for .uk domain names) to the legal owner (the registrant) of any .uk domain name.
Domains which receive letters from Nominet have the following endings: .co.uk .me.uk .org.uk .ltd.uk and .plc.uk.
When you receive a Confirmation of Registration letter, please complete and return the reply form, posting it directly to Nominet. This helps ensure that Nominet hold the correct details for your domain name on their registry databases. Further information can be found at http://www.nic.uk/registrants/onlineservices/faq/.
What about other domain names?
Confirmation of Registration letters are only sent out to registrants of .uk domain names. Non .uk domain names (such as .com .net .org .info .eu .uk.com and .uk.net) are not registered via Nominet, and don't receive a Confirmation of Registration letter.
Please note: Possession of a current Confirmation of Registration letter does not necessarily confirm legal ownership of a domain name – for example, when you transfer a domain name after your letter has been posted.