Certificate of Sponsorship

A Certificate of Sponsorship (COS) is an electronic document with a unique reference number that is given to the sponsored work visa applicant by their sponsor.

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A COS is needed by individuals applying for UK leave to enter or remain under UK-sponsored work visa categories, including: 

There are two types of COS, "defined" and "undefined". Here are the key differences between the two:


A defined COS is associated with a specific job offer from a UK employer. It is issued when an employer in the UK has offered a job to a foreign national, and the applicant has been sponsored for that specific job role. The visa holder can only work in the job role specified in the COS. Changing jobs often requires obtaining a new COS. The visa holder is typically tied to the sponsoring employer, and changing employers usually necessitates a new COS and, in some cases, a new visa application.


An undefined COS does not tie the holder to a specific job role or employer. It provides more flexibility, as the visa holder can seek and change employment without the need for a new COS. The visa holder can work in various roles and sectors, and changing employers or job roles is typically easier.