Defined vs Undefined Certificate of Sponsorship: What Is the Difference?

One of the most common questions employers have after getting a Sponsor Licence is:

“Do I need a Defined or Undefined Certificate of Sponsorship?”

The names do not exactly help.

Both are Certificates of Sponsorship. Both are used by licensed employers. Both ultimately support a worker’s visa application.

But they are not interchangeable.

For Skilled Worker sponsorship, the key distinction is usually where the worker is applying from.

A worker applying for entry clearance from outside the UK will generally need a Defined Certificate of Sponsorship.

A Skilled Worker applying from inside the UK will generally need an Undefined Certificate of Sponsorship, provided they are eligible to make the relevant in-country application.

That sounds simple enough.

And for many straightforward cases, it is.

The problems usually start when an employer assumes the two certificates are basically the same thing and assigns whichever one happens to be available.

That can become a compliance issue. The current Sponsor Guidance expressly identifies assigning an Undefined Skilled Worker CoS to someone who requires a Defined CoS as a breach that can lead to sponsor action.

So this is one of those areas where a two-minute check before assignment can save considerably more trouble afterwards.

What is a Certificate of Sponsorship?

Before looking at the difference between Defined and Undefined CoS, it helps to understand what a Certificate of Sponsorship actually is.

A CoS is an electronic sponsorship record assigned by a licensed sponsor to a worker. It contains information about the worker, the job they are being sponsored to perform and the terms of the proposed employment.

Each CoS has its own unique number. The worker then uses that number when making the relevant visa application.

It is not a physical certificate.

There is no document arriving in the post.

No frame required.

The important thing is the sponsorship record itself and the information entered against it.

For employers, the CoS is where the proposed employment is formally connected to the worker’s immigration application.

That is why the correct type matters.

What is a Defined Certificate of Sponsorship?

A Defined Certificate of Sponsorship, often shortened to Defined CoS or DCoS, is used for a Skilled Worker who is applying for entry clearance from outside the UK.

The Home Office caseworker guidance is clear on this point. If the Skilled Worker application is for entry clearance, the CoS must be a Defined CoS.

A Defined CoS is not taken from the sponsor’s normal Undefined CoS allocation.

Instead, the sponsor makes a specific request through the Sponsor Management System for the particular Skilled Worker role it wants to sponsor.

Once that request is approved, the sponsor can assign the Defined CoS to the worker.

This means the process normally looks like:

• employer holds a Skilled Worker Sponsor Licence;
• employer identifies the role;
• employer requests a Defined CoS through the SMS;
• Home Office considers the request;
• Defined CoS is granted;
• employer assigns it to the worker;
• worker uses it for the entry clearance application.

The important difference is that UKVI sees the Defined CoS request before it is assigned.

What is an Undefined Certificate of Sponsorship?

An Undefined Certificate of Sponsorship is used where a Defined CoS is not required.

For Skilled Workers, this usually means a person making an eligible application from inside the UK.

Undefined CoS are also used across other Worker and Temporary Worker routes in accordance with the sponsorship rules.

Unlike Defined CoS, Undefined CoS generally come from an allocation held by the sponsor.

That means the organisation may already have a number of Undefined CoS available within its Sponsor Management System.

If it has none available, or needs more than it currently holds, the sponsor may need to make an additional allocation request.

So while the actual certificate ultimately performs a similar function, the route for obtaining it is different.

Defined vs Undefined CoS at a glance

For a straightforward Skilled Worker case, the distinction can usually be summarised as follows:

That is the simple version.

The more important version is:

check the worker’s actual immigration position before assigning anything.

The fact that somebody is physically inside the UK does not automatically mean they are eligible to make the Skilled Worker application from within the UK.

Likewise, somebody temporarily outside the UK is not necessarily treated the same way as a fresh overseas applicant in every possible circumstance.

Where the immigration history is not straightforward, check first.

Why are there two different types of CoS?

The distinction exists because the Home Office manages overseas Skilled Worker sponsorship differently from in-country sponsorship.

Defined CoS allow UKVI to see and consider the proposed overseas Skilled Worker role before the certificate is assigned.

Undefined CoS operate more like a controlled allocation held by the sponsor for eligible sponsorship activity.

From an employer’s point of view, this means one type is requested for the role, while the other is generally drawn from an allocation already held by the sponsor.

That is why knowing which type is required affects not only compliance but also timing.

If you need a Defined CoS, you need to factor the request into the recruitment process.

If you need an Undefined CoS but have no allocation left, you may need to request more before the worker can be sponsored.

How do you apply for a Defined CoS?

A licensed Skilled Worker sponsor applies through the Sponsor Management System.

The Home Office has a dedicated SMS manual covering Defined CoS requests.

The sponsor will need to provide information about the proposed job.

This can include matters such as:

• occupation code;
• job title;
• salary;
• working hours;
• start and end dates;
• job description;
• work location; and
• other relevant Skilled Worker information.

The request should therefore be prepared from the actual proposed employment.

This is not the point to guess the occupation code and tidy it up later.

The details used to request the Defined CoS need to reflect the genuine role the business intends to sponsor.

Do you need to know the worker before requesting a Defined CoS?

Not always.

The sponsor may be able to request a Defined CoS for a genuine role before the final worker has been identified, depending on the circumstances.

However, the position should not be treated as an opportunity to request certificates speculatively.

The role itself needs to be genuine and the sponsor should have a proper recruitment reason for needing the certificate.

Where a particular worker has already been identified, it is usually sensible to check their circumstances before the request is made.

That means looking at:

their immigration position

the proposed role

salary

occupation code

and whether Skilled Worker sponsorship is actually appropriate.

There is little value obtaining a Defined CoS for a role if the intended worker cannot ultimately qualify for it.

How long does a Defined CoS take?

The Home Office does not treat Defined CoS in the same way as ordinary Undefined allocation requests.

The Defined CoS process has its own consideration route through the SMS.

Straightforward requests can sometimes be dealt with quickly.

However, the Home Office may ask for more information before approving the request.

This can happen where the role, salary or business circumstances need clarification.

So if an overseas worker has a fixed start date, do not assume the Defined CoS is an instant administrative step.

Build it into the recruitment timeline.

Can a Defined CoS request be refused?

Yes.

The Home Office can refuse a Defined CoS request where it is not satisfied with the information provided or the proposed sponsorship does not meet the relevant requirements.

That does not necessarily mean the Sponsor Licence itself is lost.

It means the particular request has not been approved.

This is another reason why the job details should be checked before the request is made.

If the salary is too low, the occupation code is inappropriate or the role does not fit the Skilled Worker requirements, the answer is not to submit the request and hope UKVI sees it differently.

Fix the underlying issue first.

How do you get an Undefined CoS?

Undefined CoS generally come from the sponsor’s available allocation.

A sponsor can view its allocation through the Sponsor Management System.

If an Undefined CoS is available, it can be created and assigned through SMS.

The Home Office provides a separate SMS manual explaining how to create and assign an Undefined CoS.

If no allocation is available, the sponsor may need to request additional Undefined CoS.

This is where forward planning matters.

If the business already knows that three employees will require Skilled Worker sponsorship this year, it should not wait until the first visa deadline arrives before checking whether the allocation exists.

What is an Undefined CoS allocation?

Think of the allocation as the number of Undefined Certificates of Sponsorship the organisation is currently permitted to use.

If the sponsor has an allocation of three and has already assigned all three, it cannot simply create a fourth because another employee suddenly needs sponsorship.

It may need to request an increase.

That request is made through the Sponsor Management System.

The Home Office may ask for information explaining why the additional certificates are required.

That can include information about the proposed workers and roles.

A request therefore needs a genuine business basis.

“We would like ten because ten sounds useful”

is unlikely to be the strongest explanation.

Can you request additional Undefined CoS?

Yes.

Sponsors can request additional Undefined CoS through the SMS where more certificates are genuinely required.

There is also a priority change-of-circumstances service for eligible requests.

Importantly, the current Home Office priority guidance states that additional CoS requests made through that priority service must be for Undefined CoS only. Defined CoS requests are excluded from that service.

That distinction is worth remembering.

There is a specific process for Defined CoS.

There is a different allocation process for Undefined CoS.

Trying to use one system to solve the other problem is unlikely to save time.

What happens if you use the wrong type of CoS?

This is where the issue becomes more serious.

Assigning an Undefined Skilled Worker CoS to someone who actually requires a Defined CoS is specifically identified in the current Sponsor Guidance as a compliance breach.

So this is not simply:

“Oops, wrong dropdown.”

The type of CoS matters to the integrity of the sponsorship process.

The worker’s visa application can also be affected because the Skilled Worker caseworker guidance requires a Defined CoS for entry clearance applications.

If you discover that the wrong certificate has been assigned, get the position checked before trying to correct it through guesswork.

The appropriate response depends on what has happened and whether the worker has already made their visa application.

Does the worker’s nationality decide which CoS is needed?

No.

The distinction is not based on whether the worker is Indian, American, Nigerian, Pakistani or from any other particular country.

For Skilled Worker sponsorship, the central question is usually where the immigration application is being made.

An American worker applying for Skilled Worker entry clearance from the United States generally needs a Defined CoS.

An Indian national already in the UK making an eligible in-country Skilled Worker application generally needs an Undefined CoS.

Nationality is not what makes one certificate defined and the other undefined.

Does the worker’s current visa matter?

Yes.

This is particularly important for workers applying from inside the UK.

Being physically present in the UK does not automatically mean someone can switch into the Skilled Worker route from within the country.

The Immigration Rules contain restrictions affecting certain categories of permission.

So before assigning an Undefined CoS, we would normally want to know what immigration permission the worker currently holds.

For example, businesses commonly sponsor workers moving from routes such as Graduate permission into Skilled Worker.

That can be entirely straightforward where the requirements are met.

But the correct immigration route should be established rather than assumed simply because the worker is already employed.

Graduate visa to Skilled Worker: Defined or Undefined CoS?

If the worker is in the UK on a Graduate visa and is making an eligible Skilled Worker application from inside the UK, the employer would generally use an Undefined CoS.

This is a common sponsorship scenario.

The company may already employ the person.

Their Graduate permission is approaching expiry.

The business wants to retain them permanently or for a longer period.

The employer obtains or already holds a Sponsor Licence and then uses an appropriate Undefined CoS for the in-country Skilled Worker application.

However, the fact that the worker already works for the company does not remove the need to check:

• occupation code;
• salary;
• working hours;
• genuine role;
• Skilled Worker eligibility; and
• any other relevant requirements.

The CoS type may be straightforward.

The sponsorship still needs checking.

Student visa to Skilled Worker: Defined or Undefined CoS?

Where a Student is eligible to switch into the Skilled Worker route from inside the UK, the employer would generally use an Undefined CoS.

However, Student to Skilled Worker applications have their own eligibility considerations.

The employer should not assume that because a person holds a Student visa they can immediately be sponsored at any point during their course.

The worker needs to satisfy the applicable switching requirements.

This is another example of why the CoS type is only one part of the analysis.

We need to establish:

Can this person make the application from inside the UK?

If yes, Undefined CoS may be appropriate.

If no, the sponsorship strategy may need to be different.

What if the worker is currently outside the UK?

For a new Skilled Worker applying for entry clearance from overseas, the normal position is a Defined CoS.

This applies even if the employer already knows the worker well.

For example, the person may previously have worked for the company overseas.

They may be a former UK employee.

They may even have previously held a UK visa.

The important issue is the Skilled Worker application they are now making.

If it is an entry clearance application, the case normally requires the Defined route.

Can you assign an Undefined CoS to someone overseas?

For a Skilled Worker making an overseas entry clearance application, that would generally be wrong.

The person should normally have a Defined CoS.

This is exactly the kind of mistake that can happen where a sponsor sees an available Undefined CoS in its allocation and assumes:

“We already have one, so let’s use that.”

Do not.

Availability does not determine suitability.

The certificate needs to match the worker’s application.

Can you assign a Defined CoS to someone applying inside the UK?

Again, the type should match the immigration application being made.

An eligible Skilled Worker applying for permission to stay from within the UK would normally require an Undefined CoS.

A Defined CoS is intended for Skilled Worker entry clearance.

If the worker’s circumstances have changed after a Defined request was made, check the position before assignment.

Do not simply assume that a certificate obtained for one process can be repurposed for another.

How much does a Defined CoS cost?

The CoS assignment fee is currently the same for a Skilled Worker whether the certificate is Defined or Undefined.

The current Worker CoS fee is £525.

The employer may also need to pay the Immigration Skills Charge where it applies.

That means the financial distinction between Defined and Undefined CoS is generally not the main issue.

The important differences are:

how the certificate is obtained

and

which worker/application it can be used for.

Is the Immigration Skills Charge different for Defined and Undefined CoS?

Not simply because the CoS is Defined or Undefined.

The Immigration Skills Charge depends on the sponsorship circumstances, route, sponsor size, duration and any applicable exemptions.

So two Skilled Workers could have different ISC outcomes even if both use the same type of CoS.

Likewise, one worker using a Defined CoS and another using an Undefined CoS may both attract the charge.

The CoS type and ISC should therefore be treated as separate questions.

How long is a CoS valid once assigned?

Once assigned, a Certificate of Sponsorship needs to be used within the permitted timeframe.

GOV.UK states that the worker must use the CoS to apply for their visa within three months of assignment. They must also not apply more than three months before the job start date shown on the certificate.

This applies regardless of whether the CoS is Defined or Undefined.

Timing matters.

There is little point assigning the certificate months before the worker is ready to apply.

Likewise, waiting until the very last moment creates unnecessary pressure.

Does a Defined CoS expire before assignment?

Defined CoS requests have their own validity and assignment rules once approved.

The sponsor should therefore avoid requesting certificates far earlier than genuinely necessary.

The current SMS guidance should be checked at the time of the request because sponsor processes and validity periods can change.

The practical principle is simple.

Request the Defined CoS when there is a genuine sponsorship need and a realistic plan to assign it.

Do not collect them like supermarket vouchers.

Can a Defined CoS be used for a different job?

A Defined CoS request is linked to the role for which it was requested.

If the job changes materially before assignment, the sponsor should not assume the certificate can simply be used regardless.

This is particularly important where there is a change to:

• occupation code;
• salary;
• working hours;
• job duties; or
• other material sponsorship information.

The certificate needs to reflect the real sponsored employment.

If the role has changed substantially, check whether a fresh request is needed.

Can an Undefined CoS be used for any employee?

No.

Having an available Undefined CoS does not mean it can be assigned to any person the company chooses.

The worker and job must still satisfy the relevant immigration route.

The sponsor should check the proposed employment before assignment.

For a Skilled Worker, that means matters including:

occupation;

salary;

working hours;

genuine vacancy;

and worker eligibility.

An Undefined CoS is sponsorship capacity.

It is not permission to ignore the Skilled Worker Rules.

Who assigns the CoS?

The practical assignment is completed through the Sponsor Management System by an appropriately authorised user.

For many sponsors this will be a Level 1 User.

The Home Office provides specific SMS manuals for creating and assigning CoS and for applying for Defined CoS.

This is where a distinction we have made elsewhere becomes important.

Using the SMS is not necessarily difficult.

Knowing what information should go into it is where professional sponsorship knowledge becomes valuable.

The system might ask for the salary.

Typing £40,000 is easy.

Knowing whether £40,000 actually satisfies the Skilled Worker salary requirement for that worker and occupation is the important part.

What should you check before assigning either type of CoS?

Before assigning a Defined or Undefined CoS, we would normally want the employer to be confident about the underlying sponsorship.

That means checking the worker, role and relevant immigration requirements together.

At a minimum, consider:

• which type of CoS is required;
• the worker’s current immigration position;
• whether an in-country application is permitted where relevant;
• occupation code;
• salary;
• working hours;
• employment start date;
• job duties;
• genuine vacancy;
• Immigration Skills Charge; and
• any route-specific provisions.

If the business is already going to the trouble and expense of sponsorship, it makes little sense to rush the point where all of that information is formally recorded.

A practical example: worker overseas

Imagine a UK engineering company has recruited an experienced engineer currently living in Dubai.

The company already holds a Skilled Worker Sponsor Licence.

The worker will apply for a Skilled Worker visa from outside the UK.

The normal position is:

Defined CoS

The employer requests the Defined CoS through SMS for the proposed engineering role.

Once approved, it assigns the certificate to the worker.

The worker then uses that CoS for their Skilled Worker entry clearance application.

Straightforward.

A practical example: Graduate visa employee

Now take a UK marketing company with an employee already working for it on a Graduate visa.

Their Graduate permission expires in six months.

The company wants to retain them as a Skilled Worker.

Assuming they are eligible to switch from within the UK:

Undefined CoS

The employer checks its available Undefined CoS allocation.

If one is available, the business can prepare and assign the certificate once the sponsorship position has been checked.

If no allocation is available, the company may need to request an additional Undefined CoS.

The worker can then use the assigned certificate for their in-country Skilled Worker application.

A practical example: no Undefined allocation left

Suppose a sponsor has already used its entire Undefined CoS allocation.

Another employee now needs sponsorship.

This does not automatically mean the employee cannot be sponsored.

The employer may need to request an increase to its Undefined allocation.

It should be prepared to explain why the additional certificate is required and provide relevant information about the intended sponsorship.

Where timing is important, an eligible additional Undefined CoS request may potentially use the Home Office priority change-of-circumstances service.

This is another reason to check allocations in advance.

Visa expiry dates are predictable.

There is very little glory in discovering your allocation is zero the afternoon before one.

Common Defined and Undefined CoS mistakes

The mistakes we see employers worry about are usually not complicated.

They are often basic things that were never checked properly.

Common risks include:

• assigning an Undefined CoS to a worker who requires a Defined CoS;
• assuming location alone determines whether the worker can switch inside the UK;
• requesting a Defined CoS using an incorrect occupation code;
• entering salary information without checking the applicable threshold;
• failing to check available Undefined allocation;
• assigning a CoS too early;
• assuming the certificate guarantees the visa;
• using employment details that do not match the real job; and
• trying to correct a material error only after the worker has applied.

None of these require a wildly complicated immigration case.

Most require somebody to stop for a moment and check the sponsorship properly before assignment.

Should you get professional help with a Defined or Undefined CoS?

A licensed sponsor can manage Certificates of Sponsorship itself.

For a business that regularly sponsors workers and has experienced immigration or HR staff, that may be perfectly sensible.

For an employer sponsoring its first or second worker, professional assistance can be much more cost-effective.

The important part is not selecting “Defined” or “Undefined” from a screen.

It is making sure the entire sponsorship behind that selection works.

A professional review can look at:

• worker’s immigration status;
• place of application;
• occupation code;
• salary;
• working hours;
• CoS type;
• CoS allocation;
• start date;
• ISC liability; and
• wider Skilled Worker eligibility.

That is where the value sits.

You are not paying somebody because clicking Assign CoS is technically difficult.

You are paying because the information attached to that click matters.

Defined or Undefined CoS: the simple rule

For most straightforward Skilled Worker cases, remember:

Outside the UK

Defined CoS

Inside the UK

Undefined CoS

Then add one important sentence:

provided the worker is eligible to make the immigration application from that location.

That final part is where employers should avoid making assumptions.

If you are unsure, check before assigning the certificate.

It is considerably easier to confirm the correct CoS first than to explain later why the wrong one was used.

Need help with a Defined or Undefined CoS?

If your business already holds a Sponsor Licence and is ready to sponsor a worker, we can review the proposed sponsorship before the CoS is assigned.

That can include checking the worker’s current immigration position, whether a Defined or Undefined CoS is required, the proposed role, occupation code, salary, working hours and any Immigration Skills Charge implications.

Where additional Undefined CoS allocation is required, that can also be considered as part of the sponsorship process.

If the worker is overseas, we can look at the Defined CoS position before the request is made.

For first-time sponsors in particular, professional assistance can take away much of the uncertainty around the process and reduce the risk of avoidable errors.

Defined and Undefined CoS sound more mysterious than they really are.

The trick is simply making sure you use the right one for the right worker.

The Home Office tends to appreciate that sort of thing.

FAQs

1. What is the difference between a Defined and Undefined CoS?

For Skilled Worker sponsorship, a Defined CoS is generally required where the worker is applying for entry clearance from outside the UK. An Undefined CoS is generally used where an eligible Skilled Worker is applying from inside the UK. The correct type should always be established before the Certificate of Sponsorship is assigned.

2. Do I need a Defined CoS for a worker outside the UK?

Usually, yes. A Skilled Worker making an entry clearance application from outside the UK normally requires a Defined Certificate of Sponsorship. The employer requests the Defined CoS through the Sponsor Management System and, once approved, assigns it to the worker. The worker can then use the CoS reference for their Skilled Worker application.

3. Do I need an Undefined CoS for a worker already in the UK?

Usually, where the worker is eligible to make their Skilled Worker application from within the UK. Simply being physically present in the UK does not necessarily mean an in-country application is permitted. Employers should therefore check the worker’s existing immigration permission and switching eligibility before assigning an Undefined Certificate of Sponsorship.

4. Does a Graduate visa holder need a Defined or Undefined CoS?

A Graduate visa holder making an eligible Skilled Worker application from inside the UK would normally require an Undefined CoS. The employer must still check the proposed occupation, salary, working hours and other Skilled Worker requirements. Holding a Graduate visa does not itself guarantee that the proposed job meets the requirements for Skilled Worker sponsorship.

5. How do I get a Defined Certificate of Sponsorship?

A licensed Skilled Worker sponsor requests a Defined CoS through the Sponsor Management System. Information about the proposed employment must be provided, including relevant details about the job and salary. Once the request is approved, the sponsor can assign the Defined CoS to the worker who will use it for their entry clearance application.

6. What happens if I have no Undefined CoS available?

If your current Undefined CoS allocation has been exhausted, you may need to request additional allocation through the Sponsor Management System. The Home Office may require an explanation and supporting information about why further certificates are needed. Employers should therefore check their allocation well before an employee’s existing immigration permission is due to expire.

7. Can I use an Undefined CoS for someone applying from overseas?

A Skilled Worker making an entry clearance application from overseas normally requires a Defined CoS. Using an Undefined CoS simply because the sponsor already has one available is not an appropriate substitute. The type of certificate must correspond with the immigration application being made, and using the wrong type can create sponsorship and visa problems.

8. Does a Defined CoS cost more than an Undefined CoS?

No. For Skilled Worker sponsorship, the current Certificate of Sponsorship assignment fee is £525 regardless of whether the certificate is Defined or Undefined. Other employer costs, particularly the Immigration Skills Charge, may also apply. Those costs depend on the circumstances of the sponsorship rather than simply whether the CoS is Defined or Undefined.

9. How long does a Certificate of Sponsorship last?

Once assigned, a Certificate of Sponsorship normally needs to be used for the worker’s visa application within three months. There are also rules concerning how early the worker can apply in relation to the employment start date shown on the CoS. Employers should therefore coordinate assignment with the worker’s intended visa application timetable.

10. Should I get professional help before assigning a CoS?

For first-time sponsors, it can be particularly useful. The technical act of assigning a CoS is only one part of the process. The worker’s immigration position, occupation code, salary, working hours, CoS type and other Skilled Worker requirements should be checked first. Correcting problems afterwards can be considerably more difficult than preventing them.