Certificate of Sponsorship UK — What It Is and How to Use It

A Certificate of Sponsorship is a digital record in the Home Office's Sponsorship Management System (SMS). It is not a letter, a physical certificate, or an email — it is an entry in a government database that links your personal details to a specific job offer from a licensed sponsor. Once created, the CoS is assigned a unique alphanumeric reference number, and it is this reference number that you submit when you apply for your visa.

Think of it as the formal, official job offer that the Home Office can verify directly with the employer. It tells the caseworker reviewing your application exactly what role you are being hired for, what salary you will be paid, when you are expected to start, and which sponsor is taking responsibility for your employment.

A CoS can only be created by an employer that holds an active sponsor licence. Each CoS is tied to a single worker and a single role — you cannot transfer a CoS from one person to another, and if your job title or salary changes significantly after the CoS is assigned, the employer may need to create a new one.

There are two types of CoS: Assigned and Defined. An Assigned CoS is used when you are applying for a visa from outside the UK, or when you are extending or switching inside the UK and your employer has already been allocated a CoS allocation. An Assigned CoS is created by the employer directly from their allocation of CoS certificates — most employers have an annual allocation they can draw on.

A Defined CoS is required in specific circumstances — for example, when a worker earns above a certain salary threshold (currently above £73,900) or when an employer needs a CoS outside their standard allocation. Defined CoS requests require the employer to submit additional details to the Home Office before the CoS can be created, and they take longer to process.

For most skilled worker applications, an Assigned CoS is sufficient. Your employer's HR or sponsorship team will create it through their SMS portal once you have accepted the job offer.

A CoS contains key details about both you and the job offer: your full name, date of birth, and nationality; the job title and SOC code; the annual salary (this must match what you are actually going to be paid — it cannot be inflated to meet the threshold and then adjusted later); the proposed start date; the employer's name, address, and sponsor licence number; and any applicable working hours or shift pattern information.

The salary figure on the CoS is particularly important. If the salary on your CoS is £40,000 but the Home Office determines your SOC code has a going rate of £42,000, your application could be refused. Your employer is responsible for ensuring the salary stated is accurate and meets the threshold for your specific occupation code.

The CoS also has an expiry date — typically three months from the date it is assigned. You must submit your visa application within this three-month window. If you miss it, the employer will need to create a new CoS.

Once your employer has created your CoS in the SMS, they will give you the CoS reference number — a string of letters and numbers that looks something like X1Y2Z3W4A5B6C7D8 (the exact format varies). This is the only thing you need from the CoS itself; you do not receive any other document.

When you apply for your Skilled Worker visa online at gov.uk, you will be asked to enter this reference number. The Home Office system retrieves the CoS record automatically and links it to your application. You will then need to confirm that the details in the CoS match your understanding of the job offer.

Keep the reference number safe and double-check it carefully before submitting. Typos in CoS reference numbers are a common cause of unnecessary delays. You should also make sure the CoS has not expired before you submit — the three-month window from assignment starts from the date the employer created it, not from the date they gave you the number.

The most frequent CoS errors are: an incorrect salary figure (either too low to meet the threshold, or not matching what you were actually offered); an incorrect job title or SOC code; a start date that has passed by the time the visa is processed; and personal details that do not match your passport exactly. Any discrepancy between the CoS and your supporting documents can trigger a request for further information or, in serious cases, a refusal.

If you spot an error in your CoS details after your employer has assigned it, you need to tell them immediately. Employers can make certain amendments to a CoS through the SMS, but there are limits on what can be changed after assignment. In some cases, the employer may need to withdraw the CoS and create a new one.

Always ask your employer to share the CoS details with you before you submit your visa application so you can check every field. It is much easier to correct an error at this stage than to deal with it after a refusal.

If you are still in the process of finding a sponsor, CoS activity data is one of the most useful signals available to you. An employer that has issued a high number of CoS in recent months is clearly experienced with the sponsorship process and actively hiring internationally — both of which reduce the risk of administrative delays or last-minute problems.

The VisaAtlas sponsor search shows CoS activity for each licensed employer, allowing you to filter and sort by recent issuance. Combining this with other filters — such as city, industry, and sponsor rating — gives you a shortlist of employers most likely to be both willing and well-equipped to sponsor you.

You can also use the VisaAtlas jobs board to see live vacancies from sponsors with recent CoS history, connecting the employer research step directly to active job listings.