A Certificate of Sponsorship (CoS) is a unique digital reference number that a licensed UK employer issues to you for a specific job. It is not a physical document — it's a record created in the Home Office system that confirms your job title, salary, and start date. You need a valid CoS before you can apply for your Skilled Worker visa, and it must be used within three months of being assigned.
The Certificate of Sponsorship confuses almost everyone the first time — mostly because the name makes it sound like a certificate you can hold, frame, or download. It isn't. This plain-English guide explains what a CoS actually is, what's inside it, the difference between the two types, and exactly when and how you get one as part of a UK sponsored job.
A CoS is a reference number, not a document
The single most useful thing to understand: a CoS is a reference number, generated when your employer records the details of your job in the Home Office's Sponsor Management System (SMS). Your employer gives you that reference, and you enter it into your visa application. There's no paper certificate and nothing to carry around — the ‘certificate’ lives entirely as a digital record the Home Office can look up.
What information a CoS contains
When your employer assigns a CoS, they record the specifics of your role. These details must match your visa application and your actual job, so it's worth checking them carefully:
- Your personal details — name, date of birth, nationality, and passport information.
- The job title and its Standard Occupational Classification (SOC) code, which sets the ‘going rate’.
- Your salary, which must meet the relevant threshold for the role.
- The employment start and end dates.
- The sponsor's details and licence information.
- A unique CoS reference number you'll use in your application.
Defined vs undefined CoS
There are two types of Certificate of Sponsorship, and which one you need depends on where you're applying from:
| Type | When it's used | How the employer gets it |
|---|---|---|
| Defined CoS | Skilled Worker applicants applying from outside the UK | Requested from the Home Office for the specific role, usually decided within about one working day |
| Undefined CoS | People already in the UK switching into or extending a Skilled Worker visa (and some other routes) | Assigned from the sponsor's annual allocation of certificates |
When and how you get a CoS
A CoS comes after a job offer, not before. Once an employer decides to sponsor you, they assign the CoS through the Sponsor Management System — for applicants outside the UK, requesting a defined CoS is typically decided within around one working day. You then have three months from the date it's assigned to use it in your visa application, so timing matters: it's usually assigned close to when you're ready to apply, not months in advance.
What to check on your CoS before you apply
Because the details on your CoS must line up with your visa application, check them before you submit and raise anything wrong with your employer straight away:
- Your name, date of birth, and passport number are correct and match your passport exactly.
- The job title and SOC code reflect the role you were actually offered.
- The salary meets the threshold for the role — cross-check it against the current rules.
- The start date and CoS reference number are present and correct.
The salary point is the one most worth double-checking. If the figure on your CoS falls below the required threshold, your application can fail — see our guide to Skilled Worker visa salary thresholds for 2026 to confirm the number for your role.
CoS vs sponsor licence vs visa: how they fit together
Three things get confused constantly, so it's worth separating them. A sponsor licence is permission the Home Office grants to an employer to hire workers from outside the UK labour market. A Certificate of Sponsorship is what that licensed employer issues to you for one specific job. And the visa is what you apply for — using the CoS — to actually live and work in the UK. In short: the licence lets the employer sponsor, the CoS ties you to a role, and the visa is your permission to be here.
The order matters. An employer needs the licence before they can assign a CoS, and you need the CoS before you can apply for the visa. That's why the very first thing to check about any ‘sponsored’ job is whether the employer actually holds a licence — see how to check if a UK employer can sponsor your visa.
What a Certificate of Sponsorship costs — and who pays
Sponsorship costs are split between you and your employer, and knowing which is which protects you from being overcharged. The employer pays the costs of sponsoring — the CoS fee and the Immigration Skills Charge. As the worker, you normally pay your own visa application fee and the Immigration Health Surcharge.
| Cost | Who pays | Approximate amount (2026) |
|---|---|---|
| Certificate of Sponsorship fee | Your employer | £525 for each CoS assigned |
| Immigration Skills Charge | Your employer — cannot be charged to you | £1,320 per year (medium/large sponsors); £480 per year (small or charitable sponsors) |
| Skilled Worker visa application fee | You | Varies by visa length and role — check the current fee on GOV.UK |
| Immigration Health Surcharge (IHS) | You | Around £1,035 per year of your visa (exempt on the Health and Care Worker visa) |
Can an employer ask you to pay for your CoS?
This is where you need to be careful. By law, your employer must pay the Immigration Skills Charge themselves — the Home Office can revoke a sponsor's licence if they try to recover it from the worker. Many sponsors also cover the CoS fee. What you can legitimately be asked to pay is your own visa application fee and the Immigration Health Surcharge, plus personal costs like your TB test or travel.
Why a CoS — or the visa that follows — can be refused
A Certificate of Sponsorship isn't a guarantee. The Home Office still assesses your visa application, and problems tied to the CoS are among the most common reasons things go wrong:
- The salary recorded is below the required threshold for the role — cross-check it against the current rules before you apply.
- The SOC (occupation) code doesn't fit the actual job, or the going rate for that code hasn't been met.
- Personal details on the CoS don't match your passport or your application exactly.
- The CoS expired because it wasn't used within three months of being assigned.
- The Home Office isn't satisfied the role is genuine (the ‘genuine vacancy’ test), or the sponsor has compliance problems.
- Your own eligibility isn't met — a valid CoS still can't fix gaps in English, maintenance funds, or a required TB test.
Most of these are avoidable by checking your CoS carefully and confirming the salary figure. The salary one is the most common trap — see our guide to Skilled Worker visa salary thresholds for 2026 to confirm the number for your role.
Key Certificate of Sponsorship terms
A quick glossary of the terms you'll meet around a CoS:
| Term | What it means |
|---|---|
| Sponsor licence | Home Office permission for an employer to sponsor workers from outside the UK labour market. |
| Certificate of Sponsorship (CoS) | The digital reference number a licensed employer assigns to you for one specific job. |
| Sponsor Management System (SMS) | The Home Office system employers use to request and assign certificates of sponsorship. |
| Defined CoS | For Skilled Worker applicants applying from outside the UK; requested per role from the Home Office. |
| Undefined CoS | For people already in the UK switching or extending; assigned from the sponsor's annual allocation. |
| SOC code | The Standard Occupational Classification code for your job, which sets the ‘going rate’. |
| Going rate | The minimum salary for your specific occupation code; you must be paid the higher of this or the general threshold. |
| Immigration Skills Charge | A fee the employer pays for sponsoring you — it cannot legally be passed on to the worker. |
| Immigration Health Surcharge (IHS) | A fee you pay for NHS access for the length of your visa; exempt on the Health and Care Worker visa. |
| A-rating / B-rating | A sponsor's compliance status on the register — an A-rating is full compliance; a B-rating means an action plan. |
Where the CoS fits in the bigger picture
The Certificate of Sponsorship is the bridge between getting a sponsored job offer and applying for your visa — the last step before the application itself. It only exists once you've found a licensed employer willing to hire you, which is where most of the effort really goes. For the full journey, see our full guide to how UK sponsorship works. And to get to a CoS in the first place, create a free Hirely profile — every role we surface is from an employer with an active sponsor licence, so a genuine offer can actually lead to one.