If you are an employer sponsoring an overseas worker, choosing among defined vs undefined certificate of sponsorship can affect whether the worker can proceed with their UK visa application.
In simple terms, a Defined CoS is required for a Skilled Worker applying for entry clearance from outside the UK, while an Undefined CoS is used for a Skilled Worker applying for permission to stay from within the UK. Undefined CoS are also used on other Worker and Temporary Worker routes.
Understanding the defined vs undefined certificate of sponsorship distinction is therefore important for both employers and skilled worker visa applicants. The wrong type can create serious sponsorship problems and may lead to compliance action against the employer.
A Certificate of Sponsorship is not a physical document. It is a digital record created through the Sponsor Management System (SMS), containing information about the sponsored worker and their role.
For a UK employer, the CoS process begins after obtaining the appropriate sponsor licence. Salam Immigration helps businesses understand UK visa sponsorship requirements, including sponsor licence applications and support for international workers.
Defined vs Undefined Certificate of Sponsorship: Key Differences
The easiest way to understand the defined vs undefined certificate of sponsorship distinction is to look at the worker’s immigration application and visa route.
| Factor | Defined CoS | Undefined CoS |
| Main use | Skilled Worker applying from outside the UK | Skilled Worker applying from inside the UK, plus other eligible Worker and Temporary Worker routes |
| Allocation | No annual allocation | Annual allocation applies |
| Employer request | Case-by-case request | Allocation requested through the SMS |
| Home Office approval | Required before assignment | Allocation is granted before certificates can be assigned |
| Main applicants | Overseas Skilled Worker applicants | In-country Skilled Workers and eligible sponsored workers on other routes |
| Management | Individual Defined CoS requests | Sponsor’s annual CoS allocation |
This comparison is central to understanding the defined and undefined certificates of sponsorship rules. The correct choice depends on the relevant visa category and where the worker is applying from.
What Is a Certificate of Sponsorship CoS?
A Certificate of Sponsorship, commonly abbreviated to CoS, is an electronic record that a licensed UK employer assigns to a worker they intend to sponsor. Despite its name, it is not a paper certificate or physical document that the worker receives in the post.
It is essentially the Home Office record confirming that a licensed sponsor is sponsoring a particular worker for a particular role under an eligible immigration route. The worker then uses the unique CoS reference number when making their visa application.
The certificate of sponsorship meaning is easiest to understand by looking at the employer’s role. A sponsor licence allows an eligible UK employer to sponsor workers, while the CoS connects that sponsorship to an individual worker and job.
For a Skilled Worker, the CoS normally contains important information such as the job title, job description, occupation code, salary details, work location and the worker’s personal details. The sponsor must ensure that the information is accurate and that the proposed employment meets the requirements of the relevant visa route.
The Home Office describes a CoS as a digital record rather than a physical document. Employers manage these records through their SMS account. This means the certificate of sponsorship UK process is primarily an employer-led digital process, although the worker needs the assigned reference when completing their visa application.
What Is the Difference Between a Sponsor Licence and a CoS?
A sponsor licence and a Certificate of Sponsorship are related but they are not the same thing.
A sponsor licence gives a licensed UK employer permission to sponsor workers under particular routes. A CoS is then assigned to an individual worker for a specific role. An employer therefore generally needs a valid sponsor licence before it can sponsor a migrant worker.
The CoS does not by itself guarantee that the worker will receive a visa. The applicant must still satisfy the requirements of the relevant immigration route, including the skilled worker eligibility, salary and English language requirements where relevant.
What Is a Defined Certificate of Sponsorship?
A Defined Certificate of Sponsorship is used for the Skilled Worker visa route with entry clearance from outside the UK. In other words, where a UK employer is sponsoring a worker who is overseas and needs permission to enter the UK for the sponsored job, the employer needs to obtain a Defined CoS first.
Who needs a Defined CoS?
A Skilled Worker applying from outside the UK needs one when their application is based on work sponsorship from a UK employer. The important factor is the worker’s intended immigration application, rather than simply their nationality.
Employers apply for Defined CoS on a case-by-case basis through the sponsorship management system.
A Defined CoS is not part of an employer’s annual CoS allocation. Instead, the employer submits a separate request when it needs to sponsor a worker who will apply for entry clearance from overseas. GOV.UK (no-follow) expressly confirms that sponsors cannot apply for an annual allocation of Defined CoS.
When Is a Defined CoS Required?
A Defined CoS is required when a Skilled Worker will apply for entry clearance from outside the UK. This could involve an overseas recruitment process where a UK employer has identified a suitable migrant worker for an eligible vacancy.
The employer needs to provide information that allows the Home Office to assess the proposed skilled worker sponsorship. This can include the role, occupation code, job description, salary and other relevant details. The information should accurately reflect the genuine vacancy because the Defined CoS is linked to the particular role described in the request.
A useful way to understand the defined vs undefined certificate of sponsorship distinction is to focus first on where the Skilled Worker will make their immigration application.
If the worker is outside the UK and will apply for entry clearance, the employer normally needs a Defined CoS. If the Skilled Worker is already in the UK and is eligible to apply for permission to stay, the employer normally uses an Undefined CoS from its allocation.
How Do Employers Apply for a Defined CoS?
The employer submits the request through its SMS account and provides the relevant information about the vacancy and sponsorship. The Home Office then considers the request before the employer can assign the Defined CoS.
An employer must wait for individual approval from the Home Office for a Defined CoS.
Defined CoS are not pre-allocated and must be justified for each assignment. The current sponsor guidance allows an employer to request more than one Defined CoS in a single application where the relevant role details are the same, but there is still no annual pool of Defined CoS from which the employer can freely assign certificates.
Defined CoS requires Home Office approval before assignment. The Home Office can reject a request where the sponsor has not provided sufficient justification, the vacancy is not sufficiently credible, the role does not meet the Skilled Worker requirements, or there are concerns about previous compliance.
This is why getting the defined vs undefined certificate of sponsorship decision right at the beginning matters. An employer should not simply select whichever CoS is available in its SMS account. The type must correspond with the worker’s application and the relevant immigration rules.
What Is an Undefined Certificate of Sponsorship?
An Undefined Certificate of Sponsorship is generally assigned from a sponsor’s annual CoS allocation. For Skilled Workers, it is used where the worker is applying for permission to stay from within the UK. It is also used for workers on other eligible Worker and Temporary Worker routes, including situations where those workers are applying for entry clearance, permission to enter or permission to stay.
This means the phrase undefined certificate of sponsorship should not be treated as simply meaning “a CoS for someone already in the UK”. That is an important distinction for employers because the rules differ depending on the visa route.
Who Needs an Undefined CoS?
For a Skilled Worker already in the UK, an Undefined CoS may be relevant when they are extending their permission or switching from another eligible visa category. For example, a worker may be moving from an eligible immigration route to the Skilled Worker route, subject to the Immigration Rules.
This can also include some workers applying for global business mobility routes or switching visa categories where permitted. A worker cannot simply rely on an existing visa such as a Student visa or Graduate visa without first checking whether the relevant visa route permits switching.
How Do Employers Get an Undefined CoS Allocation?
Undefined CoS can be assigned immediately from annual allocation. However, the employer must have sufficient CoS allocation available. If it does not, it can request an increase through the SMS.
The Home Office considers the sponsor’s circumstances when determining an appropriate allocation. It includes number of workers employed, the nature and scale of the business, its trading history and the sponsor’s previous compliance record when deciding an allocation.
Sponsors should therefore request a realistic number based on their genuine recruitment needs rather than seeking certificates without a clear business requirement.
Sponsors can request additional Undefined CoS through the SMS if their allocation is insufficient. The Home Office may ask for evidence explaining why more certificates are needed.
How Many Undefined CoS Allocations Can a Sponsor Receive?
There is no single fixed number that every licensed UK sponsor receives. The annual allocation depends on the sponsor’s circumstances and business needs.
If a sponsor expects to recruit several skilled workers, it should plan its annual allocation carefully. Unused Undefined CoS are generally valid for the allocation year and are subject to the rules governing their use and expiry.
Where additional allocation is required, the sponsor should allow sufficient time for the request to be considered rather than waiting until a worker is ready to submit their visa application.
Defined and Undefined CoS Processing Times & Validity
UK CoS processing time can differ depending on the type of CoS request and whether the sponsor requires additional allocation.
| Defined CoS Allocation Processing Time | Undefined Certificate of Sponsorship Processing Time |
| Current Home Office guidance states that applications are normally considered within one working day, although this is not a guarantee. Requests may take longer where further information or checks are required. | An employer using its existing allocation can assign an available certificate through the SMS without making a new individual Defined CoS request.However, where a sponsor needs additional allocation, the Home Office must consider the request. |
Sponsors should check the current processing information before relying on a particular timeframe or priority service. A priority service for Undefined CoS requests costs £350 for fast processing.
Certificate of Sponsorship Validity
Once assigned, a CoS has a limited validity period. A CoS is valid for three months from assignment. The worker must submit their visa application within that period. If the CoS expires before it is used, the sponsor may need to assign a new certificate, subject to the applicable rules.
A Defined CoS also has a separate deadline before assignment. Sponsors must assign a Defined CoS within 90 days of approval. This is another reason employers should coordinate the recruitment process, sponsorship management and visa application carefully.
Certificate of Sponsorship Fee and Other Sponsorship Costs
The cost of sponsorship is not limited to the CoS fee. Depending on the circumstances, an employer may need to pay the sponsor licence fee, Certificate of Sponsorship fee, Immigration Skills Charge and other applicable costs.
For a Skilled Worker, the sponsor normally pays the applicable CoS fee when assigning the certificate. Employers must pay £525 for each CoS assigned under the Skilled Worker route. While the applicant has to arrange for the relevant work visa costs.
Always check the current Home Office fee schedule because charges can change.
The Immigration Skills Charge is another important cost for many Skilled Worker and Senior or Specialist Worker sponsorships. It is generally paid by the sponsor rather than transferred to the sponsored worker. Failure to pay the Immigration Skills Charge may cause problems with the sponsorship process and can affect the visa application.
Documents Required for Certificate of Sponsorship UK
There is no universal document checklist for every CoS request because the evidence required can depend on the circumstances and type of sponsorship.
Employers should have accurate information about the sponsored worker and vacancy, including:
- The worker’s personal details.
- Job title and job description.
- Appropriate occupation code.
- Salary and working arrangements.
- Work location.
- Information supporting the genuine vacancy where required.
- Details relevant to the sponsor’s licence and sponsorship duties.
The employer should also retain appropriate records. Employers must keep detailed records for each assigned CoS and comply with their wider sponsor duties.
A CoS is a formal legal declaration when submitted to the Home Office. Providing inaccurate information can therefore create more serious consequences than a simple administrative error.
Common Employer Mistakes With Defined and Undefined CoS
Mistakes in sponsorship can delay recruitment and create problems for both employers and sponsored workers.
- Common application errors include choosing the wrong type of CoS, entering incorrect salary details and using an inappropriate occupation code.
- Another issue is treating a CoS as if it were the visa itself. A Certificate of Sponsorship does not guarantee approval. The worker must still satisfy the requirements of the relevant visa route.
- Employers should also avoid assigning a certificate before checking the worker’s circumstances. Assigning the incorrect type of CoS can result in visa application refusals.
Incorrect CoS details can lead to visa refusals and compliance audits. Employers must therefore ensure that the job description, salary, occupation code and worker’s personal details are consistent with the actual employment.
A sponsor should also maintain accurate records & meet sponsor licence management responsibilities. Failure to meet sponsor duties affects the employer’s ability to sponsor workers in the future.
Can a Defined CoS Be Changed to an Undefined CoS?
A sponsor should not assume that an approved Defined CoS can simply be converted into an Undefined CoS. The appropriate CoS type depends on the worker’s circumstances and the relevant route.
If the circumstances change, the sponsor should check the current Home Office sponsor guidance before taking action. In some situations, a new CoS may be required rather than changing an existing certificate.
The same principle applies in reverse. Employers should not assign an Undefined CoS simply because it is available if the worker requires a Defined CoS for an overseas Skilled Worker visa application.
Getting the CoS Process Right
The defined vs undefined certificate of sponsorship process is ultimately about matching the sponsorship record to the correct worker, role and immigration route.
Before assigning a certificate, an employer should confirm the worker’s location, visa category, eligibility, salary, occupation code and available CoS allocation. This helps reduce avoidable errors and gives the worker a stronger foundation for their visa application.
For employers unfamiliar with UK visa sponsorship, professional immigration advice can also help identify issues before a CoS is assigned.
Get Assistance for Sponsored Work Visa with Salam Immigration
Getting the right CoS is an important part of the UK sponsorship. Whether you are an employer applying for a sponsor licence or sponsoring a skilled worker, Salam Immigration can provide tailored guidance on the relevant visa route, sponsorship requirements and CoS process.
Our immigration team can help you understand whether a Defined or Undefined CoS is appropriate and support you with your wider UK immigration requirements.
Frequently Asked Questions
What is the difference between Defined and Undefined CoS?
A Defined CoS is generally used for a Skilled Worker applying for entry clearance from outside the UK. An Undefined CoS is generally used for a Skilled Worker applying from inside the UK and for eligible workers under other Worker and Temporary Worker routes.
How long does an Undefined CoS take?
If the employer already has sufficient Undefined CoS allocation, it can generally assign an available certificate through the Sponsor Management System. If additional allocation is needed, the sponsor must request it from the Home Office, and processing can take longer.
Can a Defined CoS be changed to an Undefined CoS?
A Defined CoS should not simply be treated as interchangeable with an Undefined CoS. If the worker’s circumstances change, the sponsor should check the current Home Office sponsor guidance to determine whether a new certificate is required.
Does a Certificate of Sponsorship guarantee a UK visa?
No. A Certificate of Sponsorship does not guarantee visa approval. The sponsored worker must independently meet the requirements of the relevant visa route, and the Home Office can refuse an application if the applicant does not satisfy the Immigration Rules.
How long is a Certificate of Sponsorship valid?
Once assigned, a CoS is generally valid for three months. The worker must submit their visa application within this period. If the certificate expires before it is used, the sponsor may need to assign a new CoS, subject to the applicable rules.
