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 has five stages. The employer must first hold a sponsor licence. They then request CoS allocation: sponsors get an annual pool of undefined CoS, while defined CoS (for entry clearance) must be applied for individually.
Once allocation is available, the employer logs into the SMS, enters the job details, salary, start date, and the worker's personal information, and generates the reference number. The worker uses that number in their visa application. UKVI then verifies the CoS is valid, unexpired, and matches the 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 general salary threshold jumped from £26,200 to £41,700. From July 2025, the minimum RQF skill level rose to RQF Level 6 (graduate level), cutting many previously eligible roles. Before assigning a CoS, employers need to confirm the job's SOC code still qualifies, otherwise the 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 and the 3-month window closes, a new CoS must be issued, eating into allocation.
- Using the wrong type. An undefined CoS for someone applying from abroad (who needs a defined CoS) means an automatic refusal.
- Salary mismatch. The salary on the CoS must match the visa application exactly. Even small discrepancies trigger refusals.
- Wrong SOC code. This is one of the most common refusal reasons. Double-check it.
- Running out of allocation. Sponsors can exhaust their undefined CoS pool. Request top-ups via the SMS before you hit zero.
Frequently Asked Questions
Can an employer cancel a CoS after it's been assigned?
They can, but only before you submit your visa application. Once your application is in, the employer cannot withdraw the CoS without you being notified.
Can a worker apply for a visa without a CoS?
No. There are zero exceptions. You need a valid CoS reference number to submit a Skilled Worker visa application.
What happens if my employer's sponsor licence is revoked after my CoS is issued?
Bad news: any pending visa application using that employer's CoS will be refused. If you already hold a visa linked to that sponsor, you get 60 days to find a new sponsor or leave the UK.
Can I use the same CoS for a different visa category?
No. Each CoS is locked to one visa route. A Skilled Worker CoS cannot be repurposed for a different category.