If you’ve been offered a Skilled Worker role in the UK, your employer will talk about issuing you a “CoS” before you can apply for your visa. It’s one of the most important documents in the whole process, and one of the least understood — here’s what it actually is and how the timing works.
What a Certificate of Sponsorship actually is
A Certificate of Sponsorship (CoS) is not a physical certificate — it’s a unique electronic reference number that a UK employer holding a sponsor licence generates inside the Home Office’s Sponsorship Management System (SMS) on your behalf. It records the job title, SOC occupation code, salary, and start date your employer is sponsoring you for. You use that reference number, plus the details it contains, when you complete your own Skilled Worker visa application. Only Home Office-licensed sponsors can issue one — if a “job offer” doesn’t come with a genuine sponsor licence, be cautious.
Defined CoS vs undefined CoS
This is the distinction that confuses most applicants, because the process differs sharply depending on where you’re applying from:
| Defined CoS | Undefined CoS | |
|---|---|---|
| Who it’s for | Applicants outside the UK applying for Skilled Worker entry clearance | Workers already in the UK switching into or within the Skilled Worker route, and some other in-country applications |
| How it’s issued | Sponsor applies to the Home Office for each one, providing job and salary details; Home Office approves it individually | Drawn from the sponsor’s pre-approved annual allocation; issued almost immediately if the sponsor has allocation left |
| Typical turnaround | Commonly same day to a few working days, but can run to 1–2 weeks if the Home Office requests more information | Near-instant, since no case-by-case Home Office approval is needed |
| What runs out | N/A — approved individually each time | The sponsor’s allocation; if it runs out, they must apply to the Home Office for more before issuing further undefined CoS |
If you’re moving to the UK from abroad for a new Skilled Worker role, you almost always need a defined CoS. If you’re already in the UK on another visa and switching employer or extending within the Skilled Worker route, your new sponsor typically issues an undefined CoS.
Timing: what happens after the CoS is issued
- Your sponsor assigns the CoS and gives you the reference number plus the specific details recorded on it (job title, SOC code, salary, start date).
- Check the details immediately against your actual offer. A mismatch between what’s on the CoS and your real salary or role is a common cause of visa refusals or delays further down the line — catch it before you apply, not after.
- The CoS is generally valid for 3 months from assignment — you must submit your visa application referencing it within that window, or your sponsor has to issue a fresh one.
- Once you’ve applied using the CoS, the visa decision itself typically takes several weeks (faster with priority services) — see our Skilled Worker visa guide for current processing times.
- You can only start the sponsored job once the visa itself is granted — the CoS alone doesn’t authorise work.
Fees: who pays what
The CoS fee itself is paid by the sponsoring employer when they assign it, and — important to know if your start date slips — it is generally non-refundable even if the CoS is later cancelled or your visa application is refused. It is separate from:
- The Skilled Worker visa application fee (paid by the worker, varies by visa length and whether you’re applying from inside or outside the UK),
- The Immigration Health Surcharge (paid upfront by the worker for the full visa period), and
- The Immigration Skills Charge (paid by the employer, per sponsored worker per year of sponsorship).
Government fee and salary threshold figures change periodically, including routine uprating — always confirm the current CoS fee, salary thresholds and Immigration Skills Charge rates on gov.uk before you or your employer budgets around them, since different sources online disagree and some are out of date. For the full current cost breakdown facing the worker, see our Skilled Worker visa cost guide.
What to do if something looks wrong
If your CoS shows a different salary, role, or SOC code than what you agreed with your employer, raise it with your sponsor’s HR or immigration team before you submit your visa application — a CoS can be withdrawn and reissued, but a visa application built on an inaccurate CoS risks refusal. This is preparation guidance, not legal advice; for anything that looks genuinely wrong or urgent, confirm with your sponsor’s immigration team or an immigration adviser regulated in the UK.
VisaMet’s document screening checks your CoS details against your visa application before you submit, and our interview-prep tools cover the kinds of questions UK entry clearance officers ask Skilled Worker applicants. Join the waitlist to get early access.
Sources: UK government Skilled Worker sponsorship guidance as summarized by immigration-law commentary (Gherson, Mondaq); sponsor-licence process guides (Jobbatical, Tarve) cross-checked against each other for the defined/undefined distinction and CoS validity window — figures for fees and salary thresholds should be confirmed directly on gov.uk given conflicting figures across secondary sources.