Certificate of Sponsorship (CoS)
A Certificate of Sponsorship is a digital reference number — not a physical certificate — that a UK-licensed employer must assign to an overseas worker before that worker can apply for a Skilled Worker visa.
In This Article
- What is a Certificate of Sponsorship?
- How does it work?
- Defined CoS vs Undefined CoS
- How long is a CoS valid?
- How much does a CoS cost?
- 2025/2026 updates
- Common mistakes to avoid
- Frequently asked questions
- Related terms
What is a Certificate of Sponsorship?
A Certificate of Sponsorship (CoS) is a unique alphanumeric reference number generated on the Home Office's Sponsorship Management System (SMS). Despite its name, it is entirely digital — there is no physical document to print or sign.
Every overseas worker applying for a Skilled Worker visa must include a valid CoS reference number in their visa application. Without it, the application cannot proceed. The CoS confirms that a licensed UK employer has offered the worker a genuine role that meets the visa route's skill and salary requirements.
The CoS is tied to one specific worker, one specific job, and one specific employer. It cannot be transferred, reused, or shared.
How does it work?
The process follows these steps:
- Employer obtains a sponsor licence — The employer must be approved by the Home Office as a licensed sponsor before it can issue any CoS.
- Employer requests CoS allocation — Sponsors receive an annual allocation of undefined CoS. For defined CoS (entry clearance), they must apply to the Home Office for each one.
- CoS is assigned to the worker — The employer logs into the SMS, enters the job details, salary, start date, and worker's personal information, then generates the CoS reference number.
- Worker receives the reference number — The employer shares the unique reference number with the worker, who uses it when submitting their visa application online.
- UKVI verifies the CoS — The Home Office checks that the CoS is valid, unexpired, and matches the job offer in the visa application.
Defined CoS vs Undefined CoS
There are two types of Certificate of Sponsorship:
| Type | Used for | Allocation |
|---|---|---|
| Defined CoS | Workers applying from outside the UK for entry clearance | Must be requested individually from the Home Office (capped pool) |
| Undefined CoS | Workers already in the UK switching visa category or extending | Assigned from the employer's annual allocation, no per-CoS approval needed |
Defined CoS applications are assessed by the Home Office before issue. There is a monthly limit on the total number available, so employers should plan ahead, especially for roles outside the Immigration Salary List.
How long is a CoS valid?
A Certificate of Sponsorship is valid for 3 months from the date it is assigned. The worker must submit their visa application before this window closes.
If the visa application is not submitted in time, the CoS expires and the employer must assign a new one. This is a common source of delays — see CoS Expiry & Validity for more detail.
Once the visa is granted, the CoS itself no longer has ongoing validity — the worker's visa leave dates take over.
How much does a CoS cost?
The CoS itself carries no direct fee for the employer to issue. However, assigning a CoS triggers the obligation to pay the Immigration Skills Charge (ISC), which costs:
- £1,000 per year for medium and large sponsors
- £364 per year for small sponsors and charities
For a standard 3-year Skilled Worker visa, a large employer pays £3,000 in Immigration Skills Charge. See Immigration Skills Charge for full details.
Workers do not pay for the CoS — it is entirely an employer cost.
2025/2026 Updates
Since April 2024, the salary threshold for most Skilled Worker roles rose significantly. From July 2025, the minimum RQF skill level for eligible roles was raised to RQF Level 6 (graduate level), which narrowed which roles can be sponsored. Employers must ensure the job's SOC code still qualifies before assigning a CoS, or the worker's visa application will be refused.
The Immigration Salary List replaced the Shortage Occupation List in April 2024, changing which roles qualify for a reduced salary threshold CoS.
Common Mistakes to Avoid
- Assigning the CoS too early. If the worker delays their visa application and the CoS expires, a new one must be issued — consuming allocation and potentially causing delays.
- Using the wrong CoS type. Assigning an undefined CoS for a worker applying from abroad (who needs a defined CoS) will result in a visa refusal.
- Incorrect salary on the CoS. The salary recorded on the CoS must match what's in the visa application exactly. Discrepancies trigger refusals.
- Wrong SOC code. Using an ineligible or incorrect SOC code is one of the most common reasons a Skilled Worker visa is refused.
- Not having allocation. Sponsors can run out of undefined CoS allocation. Request top-ups via the SMS before this happens.
Frequently Asked Questions
Can an employer cancel a CoS after it's been assigned?
Yes. Employers can withdraw an assigned CoS via the Sponsorship Management System before the worker submits their visa application. Once a visa application is submitted, the CoS cannot be withdrawn without the worker being notified.
Can a worker apply for a visa without a CoS?
No. A valid CoS reference number is a mandatory requirement for a Skilled Worker visa application. There are no exceptions.
What happens if my employer's sponsor licence is revoked after my CoS is issued?
If the sponsor's licence is revoked, any pending visa applications using their CoS will be refused. Workers on existing visas linked to that sponsor are given 60 days to find a new sponsor or leave the UK.
Can I use the same CoS for a different visa category?
No. A CoS is specific to one visa route (e.g., Skilled Worker). It cannot be repurposed for another route.
Related Terms
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