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. GOV.UK calls it an electronic record, not a physical document.
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 or shared, and once the Home Office has decided an application that used it, it cannot be used in another application.
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 Skilled Workers applying from outside the UK) 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 | Skilled Workers applying from outside the UK | Applied for through the SMS each time, and approved by the Home Office before the employer can assign it |
| Undefined CoS | Skilled Workers applying from inside the UK, and applicants on all other visas | Assigned from the employer's annual allocation, with no approval for each one |
GOV.UK says UKVI usually approves a defined certificate within one working day, though further checks can take longer. An employer that has too few undefined certificates can ask for more through the SMS. GOV.UK says it usually gets a decision within 12 weeks, or within 5 working days if it pays for the priority service.
Our page of Skilled Worker visa statistics shows how many Skilled Worker visas are granted each quarter to people applying from outside the UK, who use a defined CoS, and to people switching or extending inside it, who use an undefined one.
How long is a CoS valid?
A Certificate of Sponsorship is valid for 3 months from the date it is assigned. The worker must make a valid visa application before this window closes. They also can't apply more than 3 months before the start date on the certificate, so the employer needs to time the assignment with both limits in mind.
If the visa application is not made in time, the CoS expires and the employer must assign, and pay for, a new one. This is a common source of delays. See CoS Expiry & Validity for more detail.
Once the Home Office has decided to grant or refuse the application, the CoS shows as "used" in the employer's SMS account and can't support another application. The worker's visa dates then take over.
How much does a CoS cost?
An employer pays a fee each time it assigns a certificate. For a Skilled Worker it is £525 per certificate.
If the worker is on a Skilled Worker or Senior or Specialist Worker visa, the employer might also have to pay the Immigration Skills Charge (ISC). The amount depends on the employer's size and on how long the certificate says the worker will work for it:
- £1,320 for the first 12 months, then £660 for each additional 6 months, for medium and large sponsors
- £480 for the first 12 months, then £240 for each additional 6 months, for small and charitable sponsors
For a 3-year Skilled Worker visa, a medium or large employer pays £3,960 in Immigration Skills Charge and a small or charitable one pays £1,440. It is paid in full when the certificate is assigned, and a few occupation codes, mostly in science and research, are exempt. GOV.UK's page on the Immigration Skills Charge lists the exemptions and the refund rules.
Workers do not pay either charge. It is entirely an employer cost, and GOV.UK says an employer's licence may be revoked if it asks the worker to pay the fee or any costs linked to the application.
2025/2026 Updates
The general salary threshold was £38,700 before 22 July 2025 and has been £41,700 since then. The same rule changes raised the minimum skill level to RQF level 6 (graduate level) for most jobs, so many jobs that used to qualify no longer do. 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. A job on the list can be paid at least £33,400 instead of £41,700, but it must still be paid at least its going rate.
Common Mistakes to Avoid
- Assigning the CoS too early. If the worker delays and the 3-month window closes, the employer must assign and pay for a new one.
- Using the wrong type. GOV.UK says UKVI will normally revoke the licence of an employer that assigns an undefined CoS where a defined one is required, which is for a Skilled Worker applying from outside the UK.
- Wrong occupation code. This is a significant error: the employer has to withdraw the CoS and assign a new one, so check the code before assigning.
- Mistakes in the details. A minor error, such as a mistyped name or date of birth, can be fixed with a sponsor note while the CoS still shows as "assigned". More than one error in the worker's personal details usually means a new CoS.
- Running out of allocation. Sponsors can exhaust their undefined CoS pool. Request top-ups via the SMS before you run out, because GOV.UK says a decision usually takes up to 12 weeks.
- Asking the worker to pay. The employer pays the certificate fee and the Immigration Skills Charge, and its licence may be revoked if it asks the worker to cover them.
Frequently Asked Questions
Can an employer cancel a CoS after it's been assigned?
Yes, until it has been used in an application. The employer withdraws it in the Sponsorship Management System. UKVI refuses any application that relies on a withdrawn certificate, and the certificate fee is not refunded. The Immigration Skills Charge is refunded in full if the certificate is withdrawn before anyone uses it.
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.
Related Terms
- Defined CoS vs Undefined CoS
- Sponsor Licence
- Immigration Skills Charge (GOV.UK)
- CoS Expiry & Validity