Introduction

The UK’s immigration system is designed around sponsorship. For most non-UK nationals seeking employment in Britain, a Certificate of Sponsorship (CoS) is the linchpin of a successful visa application. It’s more than just a reference number—it’s formal confirmation that an employer is authorised to bring in overseas talent for a specific job. As of 25 July 2025, understanding how CoS works is vital for employers and applicants alike.

What is a certificate of sponsorship (CoS)

A Certificate of Sponsorship (CoS) is an electronic document issued by a UK-licensed sponsor to confirm they are offering a genuine, eligible job to a non-UK worker. Despite the name, it’s not a paper certificate but a unique alphanumeric reference number used during the visa application process.

The CoS acts as a formal declaration to the UK Home Office that the sponsor takes responsibility for the worker throughout their stay and confirms compliance with the immigration rules.

Why a CoS is essential for UK work visas

Without a valid CoS, a foreign national cannot apply for most UK work visas. It is a mandatory requirement for routes such as the Skilled Worker visa, Senior or Specialist Worker visa (Global Business Mobility), and Health and Care Worker visa.

The Home Office uses the CoS to assess whether:

• the job is eligible under the visa route

• the salary meets minimum thresholds

• the applicant is genuinely being hired to fill a legitimate vacancy

It also ties the applicant to their sponsoring employer, forming the foundation of their immigration permission.

Types of certificate of sponsorship in 2025

4.1 defined CoS

Defined CoS are used for Skilled Worker visa applicants applying from outside the UK. Each defined CoS must be individually requested and approved by the Home Office before it can be assigned. This system ensures that the government can monitor demand and ensure immigration compliance.

Once approved, the defined CoS can be assigned to the overseas applicant, who must then use it in their visa application within 3 months.

4.2 undefined CoS

Undefined CoS are used for applicants already inside the UK, such as those extending their visa, switching from another route, or continuing employment with a new sponsor.

Sponsors must estimate and request an annual allocation of undefined CoS from the Home Office. These are issued from the sponsor’s allocation without individual pre-approval.

Who can issue a CoS

Only organisations with a valid sponsor licence issued by the UK Home Office can assign Certificates of Sponsorship. These licensed sponsors must meet strict requirements regarding recruitment practices, record-keeping, and compliance monitoring.

Sponsors can be businesses, care homes, educational institutions, or multinational companies, depending on the visa route. Being a sponsor involves reporting duties and regular scrutiny by the Home Office.

Care sector sponsors must now meet enhanced compliance checks due to high risk of abuse, including providing evidence of genuine employment, PAYE registration, and HR processes.

Eligibility criteria for assigning a CoS

Before issuing a CoS, the employer must ensure:

• the job is on the list of eligible occupations

• the salary meets or exceeds the updated minimum requirement (as of July 2025, most Skilled Worker roles now require £38,700 or £15.88/hour for transitional cases, or £41,700 or £17.13/hour under the standard route, depending on the job and applicant category).

• the role is genuine and not created purely for immigration purposes

• the worker meets the English language and other visa requirements

• From July 2025, eligible Skilled Worker roles generally require RQF Level 6 (graduate-level) or above, unless listed on the Immigration Salary List or covered by transitional measures.

Failure to meet any of these criteria can result in visa refusal or licence penalties.

Information included in a CoS

A Certificate of Sponsorship contains specific and legally binding details, including:

• Sponsor licence number

• CoS reference number

• Applicant’s name and passport details

• Job title and SOC (Standard Occupational Classification) code

• Salary and working hours

• Job start and end date

• Place of work

• Confirmation of whether the CoS was assigned under the Skilled Worker route or another category

Any errors or inconsistencies in this data can lead to application delays or rejection.

Validity and expiry of a CoS

Once assigned, a CoS is valid for 3 months. The applicant must submit their visa application during this window. If they fail to do so, a new CoS may be required, including reassessment by the sponsor.

After the visa is granted, the CoS is tied to the worker’s permission to stay. Any changes in job title, duties, or employer may necessitate a new CoS and a fresh visa application.

Common mistakes and refusal reasons

Several errors can jeopardise the success of a visa application linked to a CoS, including:

• Assigning a CoS for an ineligible job

• Salary falling below threshold

• Incorrect SOC code

• Mismatched name details between passport and CoS

• Using a defined CoS for an in-country application

• Exceeding the sponsor’s annual allocation for undefined CoS

Sponsors must be meticulous. Mistakes may not only lead to refusals but also damage the sponsor’s credibility with Home Office.

How to check your CoS status

Once a CoS is assigned, applicants can view its status via their sponsor or by accessing correspondence from the Home Office. While there’s no public portal for individuals to track a CoS independently, sponsors can view assignment history through the Sponsorship Management System (SMS).

If you’re unsure whether a CoS has been assigned or used, your employer (sponsor) should confirm the status directly with you.

Latest updates as of july 2025

As of July 2025, notable updates include:

• As of 1 January 2025, Biometric Residence Permits (BRPs) are no longer issued with long validity. Migrants are now required to use their UKVI digital account (eVisa) for verification, including CoS-linked visa applications.

• Shortage Occupation List reforms: The list is expected to be restructured later in 2025, potentially altering eligibility and salary exemptions.

• More scrutiny on care sector sponsors: Due to high abuse risks, the Home Office has increased audits and suspensions in this sector.

• Digital Right to Work checks: CoS holders must undergo identity checks through the Home Office’s online checking system.

Staying up to date with guidance is essential for both sponsors and applicants to remain compliant and avoid costly delays.

Conclusion

A Certificate of Sponsorship is the backbone of the UK work visa system. It certifies the authenticity of a job offer and links a migrant’s immigration status to a licensed employer. Understanding the different types, eligibility requirements, and latest changes ensures that the sponsorship process runs smoothly. For employers, it’s a duty of care and compliance. For applicants, it’s the first formal step toward building a future in the UK.

About bs immigration

BS Immigration is a UK-based, IAA-regulated immigration consultancy. We specialise in UK work visa sponsorship, employer licence applications, and skilled worker visa solutions. Whether you’re an individual applicant or a company seeking to sponsor overseas talent, our expert team provides tailored guidance, compliance support, and full-service representation.