A Certificate of Sponsorship (CoS) is a digital record, not a physical certificate, that a licensed UK employer assigns to a worker they want to sponsor. You must hold a valid sponsor licence before you can assign one, and a Skilled Worker visa application cannot move forward without a valid CoS reference number.
What a Certificate of Sponsorship really is
A CoS is an electronic record created in the Home Office Sponsorship Management System. Each CoS has a unique reference number that the worker uses in their visa application.
The CoS confirms key details about the role, including the job title, occupation code, salary, working hours, work location and employment dates. It also links the worker’s visa application to your business as the licensed sponsor.
It is important to be clear about what a CoS is not. It is not an employment contract, and it does not guarantee that the visa will be granted. The Home Office will still assess the worker’s application, including their eligibility, salary, role, English language ability, funds where relevant, and immigration history.
If you are still weighing up whether sponsorship suits your business, our guidance on work sponsorship visa london sets out the wider picture.
You need a sponsor licence first
You cannot assign a CoS until your business has an approved sponsor licence for the relevant route. For most employers hiring overseas workers, that means the Skilled Worker route.
Many employers underestimate the sponsor licence stage. Before a licence is granted, the Home Office will assess whether your business is genuine, operating lawfully, has suitable HR systems, and can meet sponsor duties. It is worth reading our Skilled Worker sponsor licence step by step guide before you begin.
Keeping the licence in good standing matters just as much. Poor record keeping, late reporting, incorrect CoS assignment or failure to monitor sponsored workers can put your licence at risk. Our note on sponsor licence compliance in 2026 explains the common pitfalls.
If you are an individual planning to set up a company and sponsor yourself, the route works differently, and our self sponsorship visa london page covers how that is structured.
The two types of CoS
There are two main Skilled Worker CoS categories, and choosing the wrong one can cause delay or refusal.
| Type of CoS | Who it is for | How you obtain it |
| Defined CoS | Skilled Worker applicants applying from outside the UK for entry clearance | Requested individually through the Sponsorship Management System and assigned after Home Office approval |
| Undefined CoS | Workers already in the UK switching route, extending permission, changing sponsor, or certain other sponsored routes | Assigned from the annual allocation on your sponsor licence, or requested as an increase if needed |
Defined CoS requests are often processed quickly, but they are not automatically guaranteed within a day. UKVI may ask for more information before approving the request.
Before assigning either type, check that the role is eligible, the salary meets the correct threshold, and the worker meets the relevant visa requirements. Our overview of skilled worker visa eligibility sets this out in plain terms.
What it costs you
The current Worker CoS fee is £525 per certificate. This cost sits with the sponsor and must not be passed on to the worker.
You will also usually pay the Immigration Skills Charge when assigning a Skilled Worker CoS, unless an exemption applies. From 16 December 2025, the charge is £480 per year for small or charitable sponsors and £1,320 per year for medium or large sponsors, paid upfront for the full sponsored period.
Sponsors must not pass the CoS fee, Immigration Skills Charge, or prohibited sponsor-related costs on to the worker. Doing so can put the sponsor licence at risk.
If you would like to talk it through with an immigration consultant london employers trust, we are glad to help.
Click here to read Part 2 of this article.