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A Certificate of Sponsorship (CoS) is a mandatory requirement for most UK work visas that rely on employer sponsorship.?It is not a paper certificate, but a digital reference number issued by a licensed UK employer through the Home Office sponsorship system.
Understanding what a CoS is and how it works is essential for both employers sponsoring overseas workers and foreign nationals applying for UK work visas.
1. What Is a Certificate of Sponsorship (CoS)?
A Certificate of Sponsorship is an electronic record created by a UK-licensed sponsor and assigned to a specific migrant worker.
It contains key details such as:
• Job title and occupation code
• Salary and working hours
• Employer details
• Employment start and end dates
• Sponsorship reference number
The CoS confirms that the employer is offering a genuine, eligible role that meets UK immigration requirements.
2. Who Issues the Certificate of Sponsorship?
Only employers approved as licensed sponsors by the UK Home Office can issue a CoS.
• Workers cannot apply for a CoS themselves
• Recruitment agencies cannot issue a CoS unless they are the direct employer
• The employer must remain compliant throughout the sponsorship period
3. Types of Certificate of Sponsorship
Defined CoS
• Used for Skilled Worker visa applicants applying from outside the UK
• Employer must request approval from the Home Office before assigning it
Undefined CoS
• Used for applicants already inside the UK
• Also used for visa extensions and employer changes
• Issued from the sponsor’s annual CoS allocation
4. How Is a CoS Used in a Visa Application?
The process typically works as follows:
1 Employer assigns a CoS to the worker
2 Worker receives the CoS reference number
3 Worker submits a UK work visa application
4 The CoS number is entered in the visa application form
Without a valid CoS, a sponsored work visa application cannot proceed.
5. Which UK Visas Require a CoS?
A Certificate of Sponsorship is required for visas such as:
• Skilled Worker visa
• Health and Care Worker visa
• Senior or Specialist Worker visa
• Minister of Religion visa
• International Sportsperson visa
Visas like the Graduate Route or Global Talent visa do not require a CoS.
6. How Long Is a CoS Valid?
• A CoS is usually valid for 3 months from the date it is assigned
• The visa application must be submitted within this validity period
• If unused or expired, a new CoS must be issued
7. Common Reasons a CoS Is Refused or Invalid
A CoS may be rejected or cancelled if:
• Job details do not match visa requirements
• Salary does not meet the minimum threshold
• Employer loses their sponsor licence
• Incorrect occupation code is used
• False or misleading information is provided
An invalid CoS will result in visa refusal.
8. Can a CoS Be Transferred Between Employers?
No.?A Certificate of Sponsorship is employer-specific.
If a worker changes employers, the new employer must:
• Hold a valid sponsor licence
• Issue a new CoS
• Support a fresh visa application
Key Takeaway
A Certificate of Sponsorship is a core requirement for most UK work visas.?It confirms that a licensed employer is sponsoring a genuine role that meets immigration rules.?Without a valid CoS, a sponsored UK work visa cannot be granted.
Disclaimer
This article is for informational purposes only and does not constitute legal advice.?UK immigration rules and sponsorship requirements may change. Always consult official UK government guidance or a qualified professional before applying.
December 23, 2025
