Defined vs Undefined Certificate of Sponsorship
There are two types of Certificate of Sponsorship: Defined and Undefined. For Skilled Worker sponsorship, the correct type depends principally on whether the worker is applying for entry clearance from outside the UK or permission to stay from within the UK. Defined CoS are requested individually and aren't taken from the sponsor's annual Undefined CoS allocation; Undefined CoS are used from the annual allocation for in-country Skilled Workers and for the other sponsored Worker and Temporary Worker routes.
On this page
In brief
- There are two CoS types: Defined and Undefined.
- Defined = Skilled Workers applying from outside the UK; Undefined = in-UK applications and other routes.
- Choosing the correct type matters — the wrong one can invalidate the application.
- Defined CoS are requested individually; the guide explains when each applies and how to request one.
What is the difference between Defined and Undefined CoS?
Part 2 identifies two types of CoS. Defined CoS are used for Skilled Workers applying for entry clearance from outside the UK; the sponsor doesn't receive an annual allocation of them, and applies for one individually when needed. Undefined CoS are used for Skilled Workers applying for permission to stay from within the UK, and for workers on the other sponsored Worker and Temporary Worker routes; they're taken from the sponsor's annual CoS allocation.
| Question | Defined CoS | Undefined CoS |
|---|---|---|
| Main Skilled Worker use | Worker applying from outside the UK for entry clearance | Worker applying from inside the UK for permission to stay |
| Annual allocation? | No | Yes |
| Requested individually? | Yes | No — normally used from available allocation |
| Used for other Worker / Temporary Worker routes? | No | Yes |
| Detailed assignment through SMS? | Yes | Yes |
For Skilled Worker sponsorship, the worker's application location matters. Outside the UK for entry clearance → review Defined CoS. Inside the UK for permission to stay → review Undefined CoS.
When does a Skilled Worker need a Defined CoS?
A Defined CoS is used where a Skilled Worker will apply for entry clearance from outside the UK. The distinction is route-specific — it isn't simply that "all overseas workers need a Defined CoS"; it's that a Skilled Worker applying for entry clearance from outside the UK requires one.
→ Applicant-side: CoS for Skilled Worker applicants · employer overview: Certificates of Sponsorship.
When does a Skilled Worker need an Undefined CoS?
An Undefined CoS is used for a Skilled Worker applying for permission to stay from within the UK. That can include a person extending their existing Skilled Worker permission, or making another eligible in-country Skilled Worker application, subject to the relevant immigration-route rules.
Whether the worker can apply from inside the UK is a separate question. The CoS type follows from where the application is made — switching, extension and change-of-employer eligibility are decided under the Skilled Worker rules, not here. Skilled Worker visa →
What CoS type is used for routes other than Skilled Worker?
Part 2 states that Undefined CoS are used for the other sponsored Worker and Temporary Worker routes — whether the worker is applying for entry clearance, permission to enter, or permission to stay.
Defined CoS are specifically a Skilled Worker mechanism. Other sponsored Worker and Temporary Worker routes use Undefined CoS under the general Part 2 framework.
Why does choosing the correct CoS type matter?
The Home Office will normally revoke the Sponsor Licence if the sponsor assigns an Undefined CoS where a Defined CoS was required, or assigns a Defined CoS for a role other than the one described in the Defined CoS application.
Using the wrong CoS type can affect the Sponsor Licence. For Skilled Worker sponsorship, the sponsor must identify the correct CoS type before assignment and must use any approved Defined CoS only for the role described in the request.
→ revocation · assigning a CoS.
Does a Defined CoS come from the annual CoS allocation?
No. Defined CoS are not part of the sponsor's annual Undefined CoS allocation — a sponsor applies for a Defined CoS individually when needed. Undefined CoS are taken from the sponsor's annual allocation.
Request when needed
Applied for individually through the SMS.
Use from annual allocation
Drawn from the sponsor's active allocation.
→ Annual allocation rules: Certificates of Sponsorship.
How does a sponsor request a Defined CoS?
Where a sponsor needs a Defined CoS, it must make a separate application through the SMS, providing the information required by the Defined CoS request process about the intended Skilled Worker role. The Home Office assesses the request before making the Defined CoS available for assignment.
The click-by-click SMS steps sit in the separate SMS manuals — not covered here. This page covers the request concept; the technical process is in the SMS guidance. SMS →
What information must be correct in a Defined CoS request?
A Defined CoS is approved for the role described in the request, and the sponsor must not subsequently assign it for a materially different job. The detailed job information ultimately entered on the CoS must accurately reflect the sponsored role and comply with the Part 2 assignment requirements. Before requesting a Defined CoS, the employer should have clarity on the role; occupation code; duties; salary/pay; working hours; work location; intended employment dates; and any relevant route-specific requirements.
Detailed inputs: occupation codes · salary · genuine role · what's entered at assignment: assigning a CoS.
Does approval of a Defined CoS mean the worker qualifies?
No. Assigning a CoS does not guarantee the worker will receive immigration permission. The sponsor must still be satisfied that the worker appears able to meet the applicable requirements, and the worker must separately make and succeed in the immigration application.
Defined CoS approval is not Skilled Worker visa approval. The Home Office still decides the worker's immigration application separately. Skilled Worker visa →
Does an Undefined CoS need separate Home Office approval before assignment?
Undefined CoS are normally used from the sponsor's existing annual allocation rather than being individually approved through the Defined CoS request process. The sponsor still remains responsible for ensuring it has sufficient allocation; that it's permitted to assign the CoS; that the worker and role are appropriate for sponsorship; and that the information entered is accurate.
What if the sponsor has no Undefined CoS available?
If the sponsor's annual Undefined CoS allocation is insufficient — or was set to zero — the sponsor can request an increase through the SMS and must provide reasons for the request.
→ Allocation rules (renewal, increase, allocation year): Certificates of Sponsorship.
Defined or Undefined CoS: employer decision guide
Answer up to two questions and the guide points you to the CoS type to review. It doesn't confirm that the worker can apply from the location selected, or that the worker, role or sponsor meets the Skilled Worker requirements.
This decision guide identifies the CoS type to review under the general sponsor guidance. It does not confirm that the worker can apply from the location selected, or that the worker, role or sponsor meets the Skilled Worker requirements.
Common CoS type scenarios
New Skilled Worker, currently outside the UK, applying for entry clearance
→ Review Defined CoS.
Existing Skilled Worker in the UK, making an eligible permission-to-stay application
→ Review Undefined CoS.
Worker on a sponsored route other than Skilled Worker
→ Review Undefined CoS, subject to the route-specific rules.
Skilled Worker applicant outside the UK, but the sponsor only has unused Undefined allocation
→ Having Undefined allocation does not convert this into an Undefined case. Review the Defined CoS process.
Check the sponsor's rating before assigning a CoS
The sponsor generally needs an A-rating to assign CoS to new workers. A B-rated sponsor is restricted to specified continuing-worker circumstances, and a sponsor cannot assign a CoS while the licence is suspended, dormant or revoked.
Correct CoS type is only one part of assignment authority. The sponsor's current licence rating and status must also permit the CoS to be assigned.
→ licence ratings · suspension.
What should an employer check after identifying the CoS type?
Once you've identified Defined or Undefined, the next review covers: current Sponsor Licence status; relevant CoS availability/approval; worker identity and immigration position; job title; occupation code; duties; salary; hours; work location; employment dates; route-specific fields; the applicable CoS fee; the Immigration Skills Charge where relevant; and any sponsor-note/correction requirement — all of which are explained on the assignment page.
See how to assign a Certificate of Sponsorship →
How ENS can assist with Defined and Undefined CoS
We advise on which CoS type applies to the proposed sponsorship arrangement — including whether the worker is applying from inside or outside the UK for Skilled Worker purposes; reviewing Sponsor Licence and allocation status; preparing information for a Defined CoS request; reviewing proposed CoS information before assignment; identifying related salary, occupation-code or genuine-role issues; and advising on CoS errors or compliance concerns. The classification and assignment remain the licensed sponsor's responsibility.
Defined and Undefined CoS advice
The scope depends on whether you need a CoS-type review, help preparing a Defined CoS request, an assignment review or wider employer-sponsorship advice. We agree the scope and a fixed fee in writing before any work begins.
Frequently asked questions
What is a Defined Certificate of Sponsorship? +
A Defined CoS is used for a Skilled Worker who will apply for entry clearance from outside the UK. It is requested individually rather than taken from the sponsor's annual Undefined CoS allocation.
What is an Undefined Certificate of Sponsorship? +
An Undefined CoS is used for a Skilled Worker applying for permission to stay from within the UK and for workers on the other sponsored Worker and Temporary Worker routes. Undefined CoS are used from the sponsor's annual allocation.
Does a Skilled Worker applying from outside the UK need a Defined CoS? +
Yes. Under the general Part 2 rule, a Skilled Worker applying for entry clearance from outside the UK requires a Defined CoS.
Does a Skilled Worker already in the UK need an Undefined CoS? +
Where the Skilled Worker is making an eligible permission-to-stay application from within the UK, the sponsor uses an Undefined CoS. Whether the worker can make that in-country application must be checked separately under the relevant immigration rules.
Are Defined CoS included in the sponsor's annual CoS allocation? +
No. Defined CoS are requested individually when needed. The sponsor's annual CoS allocation applies to Undefined CoS.
What happens if a sponsor uses the wrong CoS type? +
The current sponsor guidance states that the Home Office will normally revoke the Sponsor Licence where a sponsor assigns an Undefined CoS when a Defined CoS is required, or assigns a Defined CoS for a job other than the one described in the Defined CoS request.
Related guidance
Applicant-side: CoS for applicants · Skilled Worker visa · salary · occupation codes.
Disclaimer. This page helps identify the CoS type under the general sponsor guidance. It does not determine whether a worker can make an in-country or entry-clearance application, or whether the role, worker or sponsor meets the relevant immigration requirements. Source: Home Office sponsor guidance — Part 2 (Sponsor a worker) — confirm the current version on GOV.UK.
Source basis: the UK Immigration Rules and the Home Office sponsor guidance for Workers and Temporary Workers (sponsor a worker, and sponsor duties and compliance) published on GOV.UK. Rules and guidance change; confirm the current version on GOV.UK before relying on it.
Choose the correct CoS before assignment
For Skilled Worker sponsorship, the Defined-versus-Undefined distinction should be resolved before the employer starts the assignment process. Skilled Workers applying from outside the UK for entry clearance use Defined CoS, while eligible in-country Skilled Worker applications use Undefined CoS. Other sponsored Worker and Temporary Worker routes use Undefined CoS under the general sponsor framework.