For a UK client who wants to sign their contract, precontract or Power of Attorney in the UK, the procedure is as follows:
1. Sign the document at a public notary’s office; the notary is legalising the UK citizen’s signature. A list of notaries can be found at: http://www.thenotariessociety.org.uk/ The notary will charge approx £120 for each document.
2. The Legalisation Office (part of Foreign and Commonwealth office) then needs to issue an apostille (legalisation certificate) which legalises the notary’s signature. This can be done over the counter or by post. Some notaries will send off the documentation for you.
The legalisation office is at:
437 Silbury Boulevard
Milton Keynes
MK9 2AH
Tel: 01908 295 111
Full details are on their website.
http://www.fco.gov.uk/en/about-us/what-we-do/services-we-deliver/legal-services/legalisation/
The fee for legalisation of each document is £30. You need to pay the relevant amount online before sending off the documents.
Please check with your lawyer, for some countries you will not need to have an apostille.