Certificate of Sponsorship (CoS) Guidance

If your business wants to sponsor a worker under a UK sponsored work route, you will normally need to assign a Certificate of Sponsorship (CoS) before that worker can apply for their visa. A CoS is a digital record created on the sponsorship system, containing a unique reference number which the worker uses in their visa application. Once assigned, it must normally be used within 3 months, and the worker must not apply more than 3 months before the start date stated on the CoS.  

For many employers, the real difficulty is not understanding that a CoS is needed. The difficulty is determining which type of CoS is required, whether the role and salary meet the route requirements, whether there is sufficient allocation available, and whether the information entered on the sponsorship system will withstand Home Office scrutiny if the case is later reviewed. The Home Office guidance makes clear that using the wrong occupation code or entering false, misleading or incorrect salary or role information can lead to delay, refusal and wider compliance consequences.  

At Angelov Solicitors, we advise UK employers on Defined Certificates of Sponsorship, Undefined Certificates of Sponsorship, Temporary Worker CoS issues, CoS allocation planning, Sponsor Management System (SMS) processes, and wider sponsor licence compliance.

What Is a Certificate of Sponsorship (CoS)?

A Certificate of Sponsorship is the sponsor’s formal confirmation to the Home Office that it wishes to sponsor a named worker for a specific role under a relevant sponsored route. It is an electronic record, not a physical document, and each CoS carries its own reference number. The worker then uses that number when making their visa application.  

A CoS is not a visa and it does not guarantee that a visa will be granted. The worker must still satisfy the requirements of the relevant immigration route, and the details recorded on the CoS must match the wider evidence and the visa application. If the Home Office concludes that the role is not genuine, the wrong occupation code has been used, or the salary or other details have been inaccurately recorded, the application may be refused and the sponsor’s compliance history may be scrutinised more closely.  

In practical terms, a CoS is one of the most sensitive parts of the sponsorship process. By assigning it, the sponsor is effectively certifying that the role is genuine, the sponsorship route is appropriate, and the key immigration requirements are met.

Which Visa Routes Need a Certificate of Sponsorship?

A CoS is required for the sponsored Worker and Temporary Worker routes. GOV.UK separates sponsor licences into two broad categories: Worker licences and Temporary Worker licences.

Worker licences cover Skilled Worker, Senior or Specialist Worker, Minister of Religion and International Sportsperson.

Temporary Worker licences cover routes such as Scale-up Worker, Creative Worker, Charity Worker, Religious Worker, Government Authorised Exchange, International Agreement, Graduate Trainee, Service Supplier, UK Expansion Worker, Secondment Worker and Seasonal Worker.  Although the Scale-up route includes a pathway into unsponsored work after the initial sponsored period, it sits within the Temporary Worker licence category for sponsor licensing purposes. 

Broadly speaking, a CoS is required for:

• Skilled Worker
• Global Business Mobility – Senior or Specialist Worker
• Global Business Mobility – Graduate Trainee
• Global Business Mobility – Service Supplier
• Global Business Mobility – UK Expansion Worker
• Global Business Mobility – Secondment Worker
• Scale-up Worker (for the sponsored stage)
• Minister of Religion
• International Sportsperson
• Creative Worker
• Charity Worker
• Religious Worker
• Government Authorised Exchange
• International Agreement
• Seasonal Worker  

Why the Certificate of Sponsorship (CoS) Matters?

The CoS is the foundation of the sponsored work application. It records the job title, occupation code, salary, work pattern, start date and other details of the role, as well as the worker’s identity information. The Home Office relies on this information when assessing whether the application meets the Immigration Rules.  

If the CoS is wrong, the case may fail even where the employer genuinely intended to sponsor the worker. Common issues include:

• selecting the wrong occupation code
• using the wrong CoS type
• salary figures that do not properly reflect the route requirements
• mismatches between the CoS and the employment contract
• unrealistic work locations, hours or duties
• assigning a CoS for a role that is not, in substance, a genuine vacancy  

In many cases, a CoS error is not treated as an isolated data-entry mistake. It can be seen by the Home Office as evidence of wider weaknesses in sponsor compliance systems.

What are Defined and Undefined Certificates of Sponsorship (CoS)?

Defined Certificate of Sponsorship

A Defined CoS is used for a Skilled Worker applicant applying from outside the UK. It is not part of an annual general allocation. Instead, the sponsor must make a specific application for the Defined CoS through the Sponsor Management System. The Home Office guidance states that this application can only be made by a Level 1 User.  

A Defined CoS is therefore route-specific and fact-specific. It is generally used where the sponsor has identified a particular overseas Skilled Worker candidate for an eligible role.

Undefined Certificate of Sponsorship

An Undefined CoS is used for:

• Skilled Worker applicants applying from inside the UK, such as switches and extensions; and
• Applicants on other sponsored work routes where the sponsor is assigning from its available allocation.  

Undefined CoS are drawn from the sponsor’s allocation rather than being individually pre-approved in the same way as Defined CoS.

Temporary Worker and Other Route CoS

Although people often speak simply of “Defined” and “Undefined” CoS, sponsors also need to think route-by-route. A sponsor must hold the appropriate licence type and assign the correct CoS under the correct category. GOV.UK separates Worker and Temporary Worker sponsorship, and the licence structure reflects that distinction.  

Common Scenarios Where a CoS Is Needed

Hiring a Skilled Worker from overseas

If you are recruiting a Skilled Worker who will apply from outside the UK, you will usually need a Defined CoS. This commonly arises where the employer has completed recruitment, selected a candidate overseas, and wants them to apply for entry clearance.  

Switching into Skilled Worker from within the UK

If a worker is already in the UK and is eligible to switch into the Skilled Worker route, the sponsor will normally need to assign an Undefined CoS, assuming it has the relevant allocation. 

Extending sponsored leave

If an existing sponsored worker is extending permission, the sponsor may need to assign a further CoS, and it is important to check whether the route, role, salary and licence position still align properly.

Temporary or project-based assignments

Where the role falls under a Temporary Worker category, or under a Global Business Mobility route such as Graduate Trainee or Service Supplier, the sponsor must ensure it holds the correct route permission and assigns the appropriate CoS under that category.  

UK Expansion Worker cases

These cases can be particularly technical because the licence structure, rating, and early-stage allocation can affect what the business is permitted to do through the system.

What are the Eligibility Requirements for Sponsors?

Before a sponsor can assign a CoS, it must usually have:

• a valid sponsor licence for the relevant route
• appropriate key personnel in place
• a genuine role which meets the route requirements
• systems capable of meeting sponsor duties and compliance obligations  

For Skilled Worker sponsorship specifically, the Home Office states that the sponsor must be able to offer employment that meets the skill level and salary requirements and is genuine. The sponsor is also responsible for paying the sponsor licence fee and associated administrative costs, and the guidance states that licences will normally be revoked if the sponsor is found to have recouped, or attempted to recoup, certain prohibited sponsorship costs from a worker sponsored on or after 31 December 2024.  

What are the Eligibility Issues for the Worker and the Role?

The CoS must reflect a role that genuinely qualifies under the chosen route. For many sponsors, the key issues are:

• whether the occupation code is correct
• whether the salary meets the route rules
• whether the job description matches the chosen code
• whether the worker is applying from inside or outside the UK
• whether the worker is actually eligible to apply under that route at that time  

The guidance specifically warns that use of the wrong occupation code can lead to delay or refusal. It also contains detailed rules about how salary must be entered, including that salary on a CoS must be stated in pounds sterling.  

How the CoS Process Works?

In broad terms, the process usually works as follows:

Step 1: Obtain the right sponsor licence

The employer must first hold the right licence for the route in question. GOV.UK distinguishes between Worker and Temporary Worker licences, and a sponsor may hold one or both depending on its needs.  

Step 2: Access and use the Sponsor Management System

Once licensed, the sponsor manages sponsorship through the SMS. This is the system used to request Defined CoS, assign available CoS, update sponsor details and report changes.

Step 3: Identify the correct CoS type

The sponsor must determine whether the case requires a Defined CoS, an Undefined CoS, or a CoS under another sponsored route category.

Step 4: Check the role and worker details carefully

Before assigning or requesting a CoS, the sponsor should verify the role, duties, salary, work location, start date and route suitability.

Step 5: Request or assign the CoS

For a Defined Skilled Worker CoS, the sponsor makes an application through SMS. For other cases, the sponsor generally assigns from available allocation if the route and allocation permit.

Step 6: Worker uses the CoS for the visa application

Once assigned, the worker uses the CoS reference number in the visa application. The application must usually be made within 3 months of assignment. 

Practical Points About Defined CoS

The Home Office guidance confirms that there is no additional fee to apply for a Defined CoS beyond the standard CoS fee.  

Sponsors often assume that a Defined CoS request is a purely administrative step. In reality, it can become a point of substantive scrutiny, particularly if the role, salary, or factual background appears unusual. In practice, it is often sensible to treat a Defined CoS request as a pre-compliance checkpoint rather than a routine form submission.

Annual Allocation and Undefined CoS Planning

Undefined CoS planning is often overlooked. Sponsors should think in advance about likely recruitment volume, in-country switching cases, extensions, and route changes. A shortage of available Undefined CoS can disrupt onboarding and create avoidable delays, even where the candidate is otherwise ready to apply.

For that reason, allocation planning is not just an administrative issue. It is part of wider workforce and immigration strategy.

Sponsor Management System and Internal Controls

Only authorised users should operate the sponsorship system, and sponsors should have clear internal responsibility for:

• who can access SMS
• who reviews draft CoS entries
• who verifies salary and occupation code selection
• who reports changes and tracks deadlines
• how evidence is stored for compliance purposes

In many businesses, CoS problems arise not because the law is misunderstood in principle, but because HR, recruitment and legal oversight are not properly aligned.

Common Certificate of Sponsorship Mistakes

The most common CoS mistakes we see include:

• Using the wrong CoS type: For example, treating an overseas Skilled Worker case as if it could proceed with an Undefined CoS rather than a Defined CoS. This can create serious issues and may also expose the sponsor to compliance action.
• Choosing the wrong occupation code: This is expressly identified in the guidance as a serious problem because it can affect both skill level and salary analysis.
• Salary errors: Salary must be entered correctly and in pounds sterling. Misstating salary or misunderstanding how the route assesses pay can lead to refusal. 
• Inconsistencies between the CoS and the contract: If the employment contract, offer letter, payroll arrangements or job description do not align with the CoS, the case becomes vulnerable.
• Delay in using the CoS: The worker must normally use the assigned CoS within 3 months. 
• Treating the CoS as a one-off form rather than part of wider sponsor compliance: The CoS is linked to record-keeping, right to work compliance, reporting duties and the sponsor’s wider licence history.

For workers switching from the Graduate route into Skilled Worker and relying on the new entrant salary threshold, particular attention is needed. A worker can only be treated as a new entrant if granting the application would not take their combined permission as a Graduate, Skilled Worker or Tier 2 migrant beyond 4 years in total. In addition, Skilled Worker permission is normally granted until 14 days after the CoS end date. Sponsors should therefore check the worker’s immigration history carefully and issue the CoS for the correct period, as an overlong CoS can inadvertently take the application outside the new entrant limit and cause delay. 

How Angelov Solicitors Can Help

We assist with:

• advice on whether a Defined, Undefined or other route-specific CoS is required
• review of the proposed role and sponsorship route
• occupation code and salary review
• Defined CoS strategy and preparation
• Undefined CoS allocation and planning issues
• SMS guidance and practical troubleshooting
• urgent advice where a CoS has already been assigned incorrectly
• wider sponsor licence compliance support

We understand that many employers need to move quickly, but a rushed CoS decision can create much greater delay later. If you need advice on a Certificate of Sponsorship, sponsor licence compliance, Defined CoS request, Undefined CoS allocation, or an urgent SMS issue, contact us via info@angelov.law with your enquiry. 

Useful Links

https://www.gov.uk/uk-visa-sponsorship-employers

https://www.gov.uk/government/collections/sponsorship-information-for-employers-and-educators 

https://www.gov.uk/uk-visa-sponsorship-employers/immigration-skills-charge