What Is a Certificate of Sponsorship (CoS) and How Does It Work?

If you're applying for a UK work visa, you'll hear the term "CoS" a lot. "We'll assign your CoS next week." "You need your CoS number to apply." "The CoS has expired."

This guide explains in plain English what a Certificate of Sponsorship is, what's in it, who pays for it, and how you use it.

This is general information, not legal advice. Fees and rules change, so check the current figures on GOV.UK.

What a CoS is

A Certificate of Sponsorship is an electronic record that your sponsor creates in the Home Office's online sponsorship system. It confirms that a licensed employer is offering you a specific job and will sponsor your visa.

Despite the name, it isn't a paper certificate. What you actually receive is a CoS reference number. You enter that number in your visa application, and the Home Office uses it to pull up the details your employer entered.

Only a licensed sponsor can assign a CoS. That's why it matters so much that your employer is on the register of licensed sponsors with an A rating.

What's in a CoS

Your sponsor fills in the details of the job and of you. A CoS usually includes:

• your name, nationality and passport details,
• the job title and the occupation code (SOC code) for the role,
• a description of the job duties,
• your salary and working hours,
• the start and end date of your employment,
• the work address,
• the visa route, such as Skilled Worker.

Check these details carefully. Your visa application must match the CoS. If the salary, job title or dates are wrong, ask your employer to fix them before you apply.

Defined and undefined CoS

There are two kinds of CoS for Skilled Worker applications:

• Defined CoS: for people applying for a Skilled Worker visa from outside the UK. The sponsor has to apply to the Home Office for each defined CoS.
• Undefined CoS: for people already in the UK, for example someone switching from another visa or extending with the same employer.

You don't need to choose. Your employer will request the right one for your situation. It helps to know the difference, though, because a defined CoS can take a little longer.

Who pays for the CoS

Your sponsor does. The employer pays the Home Office a fee for each CoS. For Skilled Worker, that fee rose to £525 in April 2025. Your employer usually also pays the Immigration Skills Charge, a yearly amount for each sponsored worker.

A sponsor must not pass these costs on to you. If an employer or agent asks you to pay for your CoS, that's a serious warning sign. See our guide to fake visa sponsorship job offers.

What you do pay yourself:

• the visa application fee,
• the Immigration Health Surcharge,
• any required tests, such as a TB test or an English language test.

Pay these to the official bodies directly, never through an employer or agent.

How long a CoS lasts

A CoS is valid for three months from the date your sponsor assigns it. You must submit your visa application within that time.

Each CoS can only be used once. If your application is refused, or the CoS expires before you apply, your employer will need to assign a new one.

There are also timing rules. You generally can't apply more than three months before your job starts. Talk to your employer about the start date so the CoS and your application line up.

How to use your CoS step by step

1. Check your employer's licence. Make sure it's on the register, A-rated and licensed for your route. Our guide on how to check if a UK company has a sponsor licence explains how.
2. Get the CoS details. Ask for the reference number and a copy of the information on the CoS.
3. Check every detail. Your name, passport, job title, salary, hours and start date must be correct.
4. Prepare your documents. Passport, proof of English, TB test if needed, and any other documents the route requires.
5. Apply online on GOV.UK. Enter your CoS number when asked.
6. Pay your fees and the Immigration Health Surcharge.
7. Prove your identity. Depending on where you are, you'll use an app or attend an appointment.

The job must meet the rules

A CoS doesn't guarantee a visa. The job and the salary must meet the rules for your route. For Skilled Worker, that includes a minimum skill level and minimum salary thresholds, which were raised in July 2025. The exact numbers depend on the job and your circumstances.

Check the current requirements on the Skilled Worker visa page, or ask a regulated adviser.

Changing jobs means a new CoS

A CoS is tied to one employer and one job. If you want to change employer, or move to a different job with the same employer in some cases, you'll usually need a new CoS and a new visa application. We cover this in how to change your sponsor employer.

Frequently asked questions

Can I check my CoS online myself? No. Only your sponsor and the Home Office can see it in the sponsorship system. You use the reference number in your application.

Can my employer withdraw my CoS? Yes. A sponsor can withdraw a CoS before you use it, for example if the job offer is cancelled.

What happens if my sponsor loses its licence after assigning my CoS? If the licence is revoked before your visa is granted, your application is likely to be refused. Check your employer's status regularly while you wait.

Is a CoS the same as a job offer? No. A job offer comes first. The CoS is the formal sponsorship step that lets you apply for the visa.

Sources

• Skilled Worker visa (GOV.UK)
• Sponsorship information for employers (GOV.UK)
• Register of licensed sponsors: workers (GOV.UK)

Last checked November 2026. Fees and rules change, so always check the latest guidance on GOV.UK.