Certificate of Sponsorship (CoS) Explained

Updated 27 March 202610 min read

What you need to know

A Certificate of Sponsorship is a digital record created by a licensed sponsor employer through the Home Office system. It confirms the job details, salary, and worker information needed for a Skilled Worker visa application. There are two types: defined (for workers outside the UK) and undefined (for workers already in the UK). The CoS is valid for 3 months and the employer pays the associated fee.

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What Is a Certificate of Sponsorship?

A Certificate of Sponsorship (CoS) is a digital record created by a UK employer through the Home Office's Sponsorship Management System (SMS). Despite the name, it is not a physical certificate or paper document. It is an electronic record with a unique reference number.

The CoS contains all the information the Home Office needs to assess the visa application, including:

  • The worker's personal details (name, date of birth, nationality)
  • The job title and occupation code (SOC code)
  • The salary and any additional allowances
  • The start date and duration of employment
  • The work location
  • The employer's details and sponsor licence number

When the worker submits their visa application, they include the CoS reference number. The Home Office uses this to access the employer's submission and verify the details.

Defined vs Undefined CoS

There are two types of CoS, and the type your employer needs depends on where you are when you apply:

Defined CoS

Used for workers who are outside the UK and need entry clearance (a visa in their passport) to come to the UK.

  • The employer must request each defined CoS individually through the SMS
  • The Home Office reviews each request and decides whether to approve it
  • There is no annual allocation; each CoS is requested and approved separately
  • Processing can take several weeks

Undefined CoS

Used for workers who are already in the UK and are switching visa categories or extending their current Skilled Worker visa.

  • Employers receive an annual allocation of undefined CoS when they obtain their sponsor licence
  • The employer can assign these without individual Home Office approval
  • If the employer uses up their allocation, they can request more
  • Assignment is instant; no waiting for approval

The information contained in both types is the same. The difference is in the process and timing.

Who Can Issue a CoS?

Only employers with a valid sponsor licence can issue a CoS. The sponsor licence is a separate approval that the employer must obtain from the Home Office before they can sponsor any workers.

You can check whether a potential employer has a sponsor licence by searching the Register of Licensed Sponsors on GOV.UK. If the employer is not on the register, they cannot sponsor you and cannot issue a CoS.

What Information Does the CoS Contain?

The CoS is a detailed record. The employer must include accurate information in the following fields:

  • Worker's details: Full name, date of birth, nationality, passport number
  • Job details: Job title, SOC (Standard Occupational Classification) code, job description
  • Salary: Annual gross salary, any guaranteed allowances, and how the salary meets the threshold
  • Work location: The address where the worker will primarily be based
  • Start date: When the employment is expected to begin
  • RLMT (if applicable): Whether the Resident Labour Market Test was conducted (for pre-2021 CoS)

Inaccurate information on the CoS can lead to visa refusal. Both the employer and the worker should verify the details before the visa application is submitted.

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Costs

The costs associated with a CoS are paid by the employer:

  • Undefined CoS: £239 per certificate (included in the sponsorship costs the employer pays).
  • Defined CoS: The fee is built into the sponsor licence process. The employer does not pay a separate per-certificate fee.
  • Immigration Skills Charge: The employer also pays the Immigration Skills Charge (£364 per year for small sponsors, £1,000 per year for medium/large sponsors), which is charged alongside the CoS.

It is illegal for the employer to pass these costs to the worker. If an employer asks you to pay for your own CoS or sponsor licence fees, this is a red flag.

Validity and Timing

A CoS is valid for 3 months from the date it is assigned. The worker must submit their visa application within this period. If the 3-month window passes without an application being made, the CoS expires and the employer must assign a new one.

Timing is important for planning:

  • The employer should assign the CoS when the worker is ready to apply
  • Do not request assignment too early, or it may expire before the application is submitted
  • For defined CoS (from outside the UK), factor in the Home Office approval time plus the 3-month validity

Common Issues with CoS

Incorrect Information

If the CoS contains errors (wrong salary, wrong SOC code, misspelled name), the visa application may be refused. The employer should double-check all details before assigning the CoS. Some errors can be corrected by the employer through the SMS, but others may require a new CoS.

CoS Expired

If you do not submit your visa application within 3 months of the CoS being assigned, it expires. The employer must assign a new CoS and may need to pay the fee again.

Employer Loses Sponsor Licence

If the employer's sponsor licence is revoked or suspended after the CoS is assigned but before the visa is granted, the visa application will be affected. The Home Office may refuse the application or curtail an existing visa.

Salary Does Not Meet the Threshold

The salary on the CoS must meet both the general threshold (£38,700 or the going rate, whichever is higher) and any applicable new entrant or Immigration Salary List thresholds. If the salary is below the required threshold, the visa will be refused. See our salary threshold guide.

The CoS Process: Step by Step

  1. Employer checks eligibility. The employer confirms the role meets the skill level and salary requirements for the Skilled Worker route.
  2. Employer creates the CoS. Through the Sponsorship Management System, the employer enters all required details and assigns the CoS to the worker.
  3. For defined CoS: Home Office reviews. The Home Office checks the details and approves or refuses the request. This can take several weeks.
  4. Worker receives CoS reference number. The employer shares the unique reference number with the worker.
  5. Worker submits visa application. The worker includes the CoS reference number in their Skilled Worker visa application within 3 months.
  6. Home Office processes the visa. The Home Office uses the CoS to verify the job details and assess the application.

For Workers: What You Need to Know

  • You cannot apply for a Skilled Worker visa without a CoS. Your employer must initiate the process.
  • Verify the details on your CoS before applying. Ask your employer to share the key information so you can check it matches your documents.
  • Apply promptly. Do not let the 3-month validity period expire.
  • Never pay for your own CoS. The employer is responsible for all sponsorship costs.
  • If your employer is not on the Register of Licensed Sponsors, they cannot issue a CoS.

This guide is general information, not immigration advice. Immigration rules change frequently. For advice on your specific situation, consult an OISC-registered adviser or immigration solicitor. Always check GOV.UK for the latest rules.

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