Know Certificate of Sponsorship

The sponsorship certificate or (CoS) is the responsibility of your sponsoring employer in the UK. It isn't actually a paper certificate, but a digital certificate from which your employer will provide you with a reference number and other information such as the agreed upon wage.

Your sponsor will need to be registered as a licensed sponsor with the UK Border Agency and apply for a certificate of sponsorship for you. The certificate will act as an assurance that you intend to undertake a particular job. 

Make sure you have made a final decision on intending to work for a potential employer before giving your personal information to them. Only one sponsor can assign a certificate to you, and once a sponsorship certificate is arranged you cannot be sponsored by any other employer for the period noted on the certificate.

If you get a sponsorship certificate, it does not guarantee that you will secure a Tier 2 visa. You must meet all the other requirements as well for this visa.