What a Certificate of Sponsorship is
A Certificate of Sponsorship (CoS) is a virtual record — not a paper document — with a unique reference number that a licensed sponsor assigns to a worker. It sets out the job, SOC code, salary and start date, and the worker uses its reference to apply for their Skilled Worker visa.
Defined vs undefined CoS
The distinction matters for how you request it. A defined CoS is for workers applying from outside the UK — you request it through the sponsor management system and it needs Home Office approval before you can assign it. An undefined CoS is for workers already in the UK who are switching or extending, and comes from your annual allocation to assign directly.
- Defined CoS — worker is outside the UK; request per case, needs Home Office approval.
- Undefined CoS — worker is already in the UK; drawn from your annual allocation.
- Both carry the same per-CoS fee and record the same job details.
Getting the SOC code and salary right
The CoS has to state the correct occupation (SOC) code and a salary that meets both the general threshold and the going rate for that code. A wrong SOC code or an under-threshold salary is a frequent cause of refusal — we verify both before a CoS is assigned.
Frequently asked questions
What is the difference between a defined and undefined certificate of sponsorship?
A defined CoS is used for a worker applying from outside the UK and needs Home Office approval before assignment; an undefined CoS is for a worker already in the UK and comes from your annual allocation. They cost the same and record the same information.
How much does a Certificate of Sponsorship cost?
There's a fixed Home Office fee per CoS assigned to a Skilled Worker, separate from the sponsor licence fee and the Immigration Skills Charge. The current figure is in our sponsor licence cost guide.
How long is a Certificate of Sponsorship valid?
A CoS must be used within a limited window after it's assigned. We time CoS assignment against the worker's visa application so it doesn't expire before it's used.
Last reviewed: 16 July 2026. This guide is general information for employers, not legal advice — final decisions rest with the Home Office / UKVI.
Sources: UK Home Office / UKVI.