An Apostille Certificate is a small certificate that can be attached to a UK document to validate official signatures or seals on the document. The Apostille is only issued once various checks have been completed to ensure the signature or seal on the document is from a recognised UK legal practitioner or official UK Body or representative of an official UK Body.
Once the Apostille Certificate has been issued to a UK document it can then be presented outside of the UK in any member country and will be accepted as a document containing legitimate legal signatures or seals.
The Apostille Certificate originates from the Hague Conference on Private International Law (la Conférence de La Haye). Member countries of the Hague Conference can agree to accept Apostille Certificates in place of any other form of legalisation or authentication. The intention is to simplify cross border laws and remove the need for various Embassy legalisation which differs from one country to another. Countries which do not recognise the Apostille Certificate usually still request a document is issued with an Apostille but will then require further legalisation through their own Embassy.