For Skilled Worker sponsorship, there are two types of Certificate of Sponsorship: Defined and Undefined.
The distinction is principally determined by where the Skilled Worker will make their immigration application.
A Defined Certificate of Sponsorship is required for a Skilled Worker applying for entry clearance from outside the UK.
An Undefined Certificate of Sponsorship is normally required for a Skilled Worker applying for permission to stay from within the UK.
Undefined Certificates are also used for workers sponsored on most other Worker and Temporary Worker routes, whether they are applying from inside or outside the UK.
That sounds like a relatively simple administrative distinction.
It deserves more care than that.
A sponsor must use the correct type of certificate. Current Home Office guidance states that assigning an Undefined CoS where a Defined CoS is required will normally lead to revocation of the sponsor licence.
The more useful question is therefore not simply which button to select in the Sponsorship Management System.
It is where the worker is applying from, whether they are permitted to make that application from there, what type of sponsorship is required and whether the business has the necessary CoS available when it needs it.
A Certificate of Sponsorship is not the sponsor licence
These concepts are often blurred together.
The sponsor licence belongs to the organisation. It gives the business Home Office permission to participate in the sponsorship system.
A Certificate of Sponsorship, or CoS, relates to an individual worker and the job they are being sponsored to perform.
The worker then uses the CoS reference when making their immigration application.
It is an electronic record rather than a physical certificate.
The Certificate contains information about the proposed employment, including matters such as the occupation, salary, working hours, dates and work location.
That information becomes part of the Home Office’s record of the sponsorship.
A CoS should therefore be the result of a considered sponsorship decision.
It is not simply a reference number needed to complete the worker’s visa form.
The Defined and Undefined distinction applies differently to Skilled Workers
This is where the terminology can initially feel more complicated than it is.
For Skilled Workers:
Outside the UK and applying for entry clearance: Defined CoS.
Inside the UK and applying for permission to stay: Undefined CoS.
For workers on the other Worker and Temporary Worker routes, Certificates are generally Undefined regardless of whether the application is being made from inside or outside the UK.
The Defined CoS system is therefore principally a feature of the Skilled Worker route.
That means a business sponsoring different categories of worker should not assume that the Defined or Undefined terminology operates identically across every route on its licence.
Physical presence in the UK is not the complete test
An employer should not stop the analysis at:
“Is the worker currently in the UK?”
The more important question is where they can lawfully make the relevant immigration application.
A person may physically be in the UK but hold an immigration status from which switching into Skilled Worker is not permitted.
If they need to leave the UK and apply for entry clearance from overseas, the sponsorship position will need to reflect that.
Similarly, the employer should understand the worker’s current immigration status before deciding that an Undefined CoS is appropriate merely because the person happens to be living or working in the UK at the time.
The CoS type should follow the immigration application.
Not the other way around.
“I would decide where and how the worker can make the Skilled Worker application before deciding which CoS is needed. The person’s physical location today does not always answer that question. Sponsorship should follow the correct immigration route, rather than trying to make the route fit whichever certificate happens to be available.”
Abdul Jabbar, Principal Immigration Adviser
What is a Defined Certificate of Sponsorship?
A Defined CoS is used for a Skilled Worker who will make an application for entry clearance from outside the UK.
Unlike Undefined Certificates, Defined CoS do not form part of an annual allocation.
The sponsor applies for them when they are needed.
A Defined CoS request can be made where the business has already identified the worker.
It can also be made before a particular worker has been chosen, provided the sponsor has an eligible role it genuinely expects to fill with someone applying from outside the UK.
That can be useful for employers recruiting internationally.
The business does not necessarily need to wait until the successful candidate has been selected before obtaining the Defined CoS approval for a known role.
But the role itself must be sufficiently established.
More than one Defined CoS can sometimes be requested together
The Home Office permits a sponsor to apply for more than one Defined CoS in a single request where the roles are genuinely the same.
The relevant role details, including matters such as occupation code, salary, job description and start date, must match.
This may be useful where a business is recruiting several people into the same position.
For example, an engineering company might genuinely need four engineers on identical terms for the same expansion programme.
That is different from requesting several Defined Certificates speculatively for unrelated jobs.
The Defined CoS request should reflect an actual sponsorship need.
How long does a Defined CoS take?
GOV.UK currently states that Defined CoS applications are usually approved within one working day.
That is a useful operational advantage.
It should not be treated as an entitlement to next-day approval.
UKVI can carry out further checks.
If the role, salary or other information requires closer scrutiny, the Defined CoS request can take longer.
This is particularly relevant where the business has given itself a narrow recruitment timetable.
A worker overseas should not be told that their visa application will definitely begin tomorrow simply because the Defined CoS request has been submitted today.
The one-working-day figure is the normal published position.
It is not a guarantee.
Defined CoS requests can themselves be scrutinised
Licence approval does not mean the Home Office stops looking at individual sponsorship decisions.
When a business applies for a Defined CoS, UKVI has information about the proposed job.
That can lead to questions.
The Home Office may want to understand whether the occupation code is appropriate, whether the role is eligible, whether the salary works or whether the job appears genuine in the context of the sponsor.
That is another reason the sponsorship assessment should happen before the request.
The Defined CoS process should not be used to test whether UKVI is willing to accept a role the employer has not properly considered.
A Defined CoS is linked to the role approved
This is an important control.
The Home Office guidance states that it will normally revoke a sponsor licence where the sponsor assigns a Defined CoS for a job other than the one described in the application for that Defined CoS.
That is a serious consequence.
Suppose the sponsor requests a Defined CoS for a particular engineering role at a stated salary.
The recruitment position later changes.
The business now wants to use that certificate for a different management role.
It should not assume that an approved Defined CoS is simply a spare certificate that can be repurposed.
The approval was based on the role described.
If the role changes materially, the sponsorship position needs to be reconsidered.
What is an Undefined Certificate of Sponsorship?
Undefined CoS operate differently.
For Skilled Worker purposes, they are normally used where the worker is applying for permission to stay from inside the UK.
They are also used across the other Worker and Temporary Worker routes, subject to the requirements of those routes.
Unlike Defined Certificates, Undefined CoS generally come from the sponsor’s annual allocation.
When a business applies for its sponsor licence, it estimates how many Undefined Certificates it expects to need during the first year.
UKVI considers that request.
If approved, the sponsor can assign certificates from the available allocation as qualifying sponsorship needs arise.
The annual allocation should reflect a genuine recruitment need
An Undefined CoS allocation is not intended to function as an unlimited stockpile.
When an organisation requests an allocation, it should be able to justify the number sought.
A business expecting to sponsor two employees should not automatically request fifty certificates because it might be useful to have them available.
Likewise, an employer planning substantial recruitment should not underestimate its requirement purely to make the initial sponsor licence application appear modest.
The appropriate number should follow realistic workforce planning.
The Home Office can request additional information before deciding the allocation.
The sponsor should be able to explain where the expected sponsorship need comes from.
Automatic annual allocations are based partly on actual use
For eligible A-rated sponsors, the Home Office can automatically renew the annual Undefined CoS allocation.
Current sponsor guidance links the new allocation to the number of certificates actually assigned during the previous CoS year.
If a sponsor had an allocation of 15 but used only 10, an eligible automatic allocation for the following year would ordinarily be 10.
If more are needed, the business can request an increase.
This is sensible.
The allocation begins to reflect the organisation’s demonstrated sponsorship activity rather than an historic estimate made years earlier.
It also means sponsors should understand the difference between the number originally allocated and the number likely to become available automatically in future years.
Not every route receives automatic allocation renewal
Automatic renewal does not apply across every sponsorship category.
Current guidance excludes certain routes, including Seasonal Worker, Secondment Worker, Service Supplier and UK Expansion Worker.
For Skilled Worker sponsorship, only Undefined CoS can form part of the annual allocation.
Defined Certificates always continue to be requested when required.
So even an established sponsor with a large annual Undefined allocation still needs to use the Defined CoS process when recruiting a Skilled Worker who will apply from overseas.
What if the business runs out of Undefined CoS?
The sponsor can request an additional allocation through the Sponsorship Management System.
This is where recruitment planning becomes important.
GOV.UK currently says an additional Undefined CoS request will usually be decided within 12 weeks.
UKVI can take longer where further checks are needed.
For a business that has already offered a job to someone whose current immigration permission is approaching expiry, twelve weeks may be commercially significant.
An additional Undefined allocation request should therefore not be left until the existing allocation reaches zero if further sponsorship is already foreseeable.
Can additional Undefined CoS be expedited?
Potentially, yes.
Eligible A-rated Worker and Temporary Worker sponsors can use the post-licence priority service for specified sponsorship management requests, including additional Undefined CoS allocations.
The current fee is £350 per priority request.
Eligible requests are considered within five working days, subject to the service conditions and the possibility of further checks.
The priority service does not guarantee approval.
Nor can it be used to prioritise Defined CoS applications. Defined CoS have their own process and normal decision timetable.
This distinction is easy to miss because both processes involve Certificates of Sponsorship.
The priority mechanisms are different.
Allocation planning is more important than the priority service
The existence of a five-working-day priority option can create a false sense of security.
Priority availability is subject to the Home Office service rules.
The request must be eligible.
It must not already be in progress or allocated to a caseworker.
The sponsor must be A-rated and fully active.
And further enquiries can still delay the decision.
Where the business already knows that several existing employees will need Skilled Worker sponsorship during the year, it is usually better to plan the allocation accordingly than rely on priority later.
Priority is useful where circumstances change.
It is not a substitute for knowing what the sponsored workforce looks like.
Defined and Undefined do not describe the worker’s importance
The terminology can make Defined CoS sound more significant.
It is not.
“Defined” does not mean the worker is more senior, the job is more valuable or the immigration application has been pre-approved.
Likewise, “Undefined” does not mean the sponsorship is uncertain.
They are simply two mechanisms for issuing sponsorship according to the type and location of the immigration application.
The same underlying Skilled Worker requirements still need to be satisfied.
The job must qualify.
The salary must qualify.
The worker must qualify.
The sponsorship must be genuine.
The correct type of CoS does not compensate for a problem with any of those underlying requirements.
Both types of CoS cost the sponsor
The current Worker Certificate of Sponsorship fee is £525.
That applies when the certificate is assigned.
The sponsor is responsible for paying that fee.
For Skilled Workers, it must not seek to recover the CoS fee or associated administrative costs from the sponsored worker.
Depending on the sponsorship, the Immigration Skills Charge may also apply.
Those costs should be understood before the CoS is assigned.
An approved Defined CoS request does not itself mean the sponsorship costs have all been paid.
Likewise, having an Undefined certificate available within the annual allocation does not make assignment free.
The allocation gives the sponsor permission to assign.
The fee becomes relevant when it actually does so.
A CoS has a limited life once assigned
Once a Certificate of Sponsorship has been assigned to a worker, timing matters.
The worker must normally use the CoS in their immigration application within three months of the date it was assigned.
They must also not make the immigration application more than three months before the employment start date recorded on the certificate.
That means the employer should not assign a CoS simply because it is available.
The worker needs to be reasonably ready to make the application.
Assigning too early can create an expiry problem.
Assigning unnecessarily late can put pressure on recruitment or the worker’s existing immigration status.
The assignment date should follow a realistic application timetable.
“An available CoS is not a reason to assign it. I would want the job checked, the worker’s position understood and the application timetable reasonably clear. Once the certificate is assigned, the clock starts. Good sponsorship includes deciding when not to press the button yet.”
Abdul Jabbar, Principal Immigration Adviser
The worker cannot simply change the job attached to the certificate
A Certificate of Sponsorship relates to particular employment.
The occupation, salary, duties and other information are not placeholders.
If the proposed employment changes before the worker applies, the sponsor should assess the significance of the change.
Some limited matters may be capable of clarification through an appropriate sponsor note.
A substantial change can require withdrawal of the existing certificate and assignment of a new one.
That assessment should happen before the worker submits the visa application.
Trying to repair a fundamentally different job after an application has already been made can create a much more difficult position.
Defined versus Undefined is not the only CoS decision
By the time a sponsor is choosing between Defined and Undefined, several other questions should already have been answered.
Is Skilled Worker the correct immigration route?
Is the occupation eligible?
Is the occupation code correct?
Does the salary meet the applicable requirements?
Is the worker eligible?
Can they apply from inside the UK, or must they apply from overseas?
Is the role genuine?
Is the intended start date realistic?
Those questions determine whether a CoS should be assigned at all.
Only then does Defined versus Undefined become meaningful.
This is why the distinction should not be delegated as a purely administrative question to whoever happens to operate the SMS.
What if the wrong CoS is assigned?
This can be serious.
The current sponsor guidance states that UKVI will normally revoke a licence where a sponsor assigns an Undefined CoS where a Defined CoS is required.
It also states that UKVI will normally revoke where a Defined CoS is assigned for a job other than the one described in the Defined CoS application.
Those are unusually strong consequences for what can look superficially like system errors.
The reason is that Defined CoS form part of the Home Office’s control over Skilled Worker entry clearance sponsorship.
The sponsor should therefore establish the correct category before assignment.
If a mistake is identified, it should not simply be ignored in the hope that the worker’s visa application will resolve it.
The position should be considered promptly.
Can a B-rated sponsor obtain Certificates of Sponsorship?
A B-rated sponsor operates under restrictions.
It cannot use the normal sponsorship system to recruit new workers while it remains B-rated.
For Defined CoS specifically, current Skilled Worker guidance states that a sponsor cannot apply for one while the licence is B-rated or suspended.
A B-rated sponsor may, within the restrictions of its action plan, be able to sponsor certain existing workers who need permission to stay.
That is a different situation from recruiting a new Skilled Worker from overseas.
The licence rating therefore matters before the organisation begins CoS planning.
A suspended sponsor cannot continue assigning sponsorship
Suspension is more restrictive.
A suspended sponsor cannot assign new Certificates of Sponsorship while the suspension remains in place.
That applies regardless of whether the organisation had an Undefined allocation available before the suspension.
Unused allocation does not override the licence status.
Likewise, a business should not assume that a previously anticipated Defined CoS request can simply continue while the licence is suspended.
The sponsor licence has to be capable of being used.
A practical way to think about the distinction
For an employer sponsoring a Skilled Worker, the sequence should be relatively simple.
First, establish the worker’s immigration position.
Will they make the Skilled Worker application from outside the UK?
If yes, consider a Defined CoS.
Will they make a valid application for permission to stay from inside the UK?
If yes, an Undefined CoS will normally be required.
Then consider availability.
For Defined CoS, does the business need to submit a request?
For Undefined CoS, does it have sufficient annual allocation?
If not, does it need an additional allocation request?
Only after that should timing become the focus.
When will the worker be ready to apply?
What start date is realistic?
Does the business need to account for a CoS allocation decision?
That sequence reduces the risk of the certificate driving the immigration strategy.
Common mistakes
Several are avoidable.
Assuming someone in the UK automatically needs an Undefined CoS
Their immigration category may not permit an in-country switch.
Using an Undefined CoS because one is already available
Availability does not determine which type is legally required.
Treating a Defined CoS as transferable between unrelated roles
The Defined approval relates to the job described.
Underestimating future Undefined allocation needs
An additional allocation request can take substantially longer than a Defined CoS request.
Relying on post-licence priority as standard workforce planning
The priority service is useful, but it should not replace sensible allocation forecasting.
Assigning a CoS before the worker is ready
The three-month validity period begins once the certificate is assigned.
Assuming CoS approval means visa approval
The worker still needs to make and succeed in their own immigration application.
Frequently asked questions
What is the difference between Defined and Undefined CoS?
A Defined CoS is required for a Skilled Worker applying for entry clearance from outside the UK.
An Undefined CoS is normally used for a Skilled Worker applying for permission to stay from inside the UK and for workers sponsored on the other Worker and Temporary Worker routes.
How long does a Defined CoS take?
GOV.UK currently states that Defined CoS applications are usually approved within one working day.
They can take longer where UKVI carries out further checks.
Does a Defined CoS come from the annual allocation?
No.
Defined Certificates are requested when required.
A sponsor cannot hold an annual allocation of Defined CoS.
How long does an additional Undefined CoS allocation take?
GOV.UK currently states that an additional Undefined CoS request will usually be decided within 12 weeks.
Further checks can extend that period.
Is there a priority service for additional Undefined CoS?
Yes, for eligible requests.
The current Worker and Temporary Worker post-licence priority service costs £350 and considers eligible additional Undefined CoS allocation requests within five working days.
Can Defined CoS requests use the £350 post-licence priority service?
No.
The current post-licence priority guidance specifically limits additional CoS allocation priority requests to Undefined CoS.
Defined CoS requests have their own process.
How much does a Skilled Worker CoS cost?
As at September 2026, the Worker CoS fee is £525.
An Immigration Skills Charge may also apply.
How long is a CoS valid after assignment?
The worker must normally use it in an immigration application within three months of the assignment date.
Can an employer recover the CoS fee from the Skilled Worker?
No.
For Skilled Worker Certificates assigned on or after 31 December 2024, the sponsor must not recover the CoS fee or associated administrative costs from the worker.
Can I use an Undefined CoS for somebody applying from overseas?
Not for a Skilled Worker who requires entry clearance.
The current sponsor guidance states that using an Undefined CoS where a Defined CoS is required will normally result in sponsor licence revocation.
The certificate should follow the immigration position
Defined and Undefined Certificates are ultimately mechanisms.
The more important work happens before either is selected.
Where will the worker apply?
Are they permitted to apply from there?
Does the job qualify?
Does the salary work?
Is the proposed employment genuine?
Is the business ready to sponsor them?
Once those matters are clear, the CoS type usually follows naturally.
The difficulty begins when a business starts from the opposite end.
It has an Undefined certificate available and tries to structure the application around it.
Or it obtains a Defined CoS for one role and later decides to use it for another.
Or it assigns sponsorship months before the worker is ready because the certificate has finally become available.
Those are not simply administrative choices.
They can affect the validity of the sponsorship and, in serious cases, the sponsor licence itself.
A Certificate of Sponsorship should therefore be assigned when the business knows what it is sponsoring, whom it is sponsoring and how that person will make the immigration application.
At that point, Defined versus Undefined becomes what it should be: the consequence of a correctly assessed sponsorship, rather than the starting point for one.
Unsure which Certificate of Sponsorship is required?
If your organisation holds a sponsor licence and is preparing to sponsor a worker, you can request a Free Case Assessment.
Tell us about the worker’s current immigration position, where they expect to make the application and the role you intend to sponsor.
We can then consider the sponsorship position and whether Knightsbridge Immigration can assist.
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