Defined vs Undefined Certificate of Sponsorship
UK sponsors assign two distinct types of Certificate of Sponsorship through the Sponsorship Management System: Defined CoS for Skilled Worker applicants who are outside the UK, and Undefined CoS for almost everyone else. Picking the wrong one invalidates the worker's visa application, so this distinction is one of the first things every Level 1 User needs to get right.
The headline difference
| Defined CoS | Undefined CoS | |
|---|---|---|
| Used for | Skilled Worker entry clearance from outside the UK | In-country switches and extensions; most non-Skilled-Worker routes |
| Approval step | Requested individually; Home Office must approve before assignment | Drawn from the sponsor's annual allocation; no per-CoS approval |
| Allocation | None — request as needed | Fixed annual pool, renewed every 5 April |
| Typical turnaround | ~1 working day for routine requests | Available immediately within allocation |
When to use a Defined CoS
A Defined CoS is required whenever a Skilled Worker applicant will apply for entry clearance from outside the UK. This includes:
- Overseas hires applying for their first Skilled Worker visa.
- Workers currently outside the UK whose previous Skilled Worker visa has expired.
- Workers applying as a Skilled Worker for the first time from any country other than the UK, regardless of nationality.
A Level 1 User submits the request through the SMS. The Home Office assesses whether the role meets the Skilled Worker requirements and either approves it (so the CoS can be assigned) or rejects it.
When to use an Undefined CoS
Undefined CoS cover everything else a sponsor licence is used for, including:
- Skilled Worker switches from another in-country visa (Graduate, Student, Dependant, etc.).
- Skilled Worker visa extensions for workers who remain with the same sponsor.
- Senior or Specialist Worker and other Global Business Mobility routes.
- Scale-up, Minister of Religion, and International Sportsperson routes.
How the annual Undefined allocation works
Every sponsor licence has a yearly Undefined CoS allocation, refreshed on 5 April. New licences are granted a number the Home Office considers reasonable for the application submitted. If the sponsor runs out before the next renewal date, a Level 1 User can request an in-year increase through the SMS — the Home Office will look at how the existing allocation was used and whether the request is justified.
Defined CoS sit outside this allocation; there is no fixed cap, only the per-request approval gate.
Common mistakes
- Assigning a Defined CoS to someone already in the UK. The visa application is automatically invalid. Use an Undefined CoS for any in-country switch.
- Assigning an Undefined CoS to an overseas Skilled Worker hire. Same outcome: invalid application, wasted fee, fresh CoS required.
- Running out of Undefined CoS at year end. Track the allocation across the year, not the day someone needs a CoS.
- Submitting a Defined request with the wrong SOC code or salary. The Home Office will reject it; the request must be resubmitted with corrected detail.
Frequently asked questions
What is the difference between a Defined and Undefined Certificate of Sponsorship?
A Defined CoS is used when a Skilled Worker applicant is applying for entry clearance from outside the UK. The sponsor must request each one individually and the Home Office must approve the request before the CoS can be assigned. An Undefined CoS is used when the worker is already in the UK and is switching into the Skilled Worker route or extending their existing visa. Undefined CoS come out of an annual allocation and the sponsor can assign them without an extra Home Office approval step.
Which routes use Undefined Certificates of Sponsorship?
Undefined CoS cover Skilled Worker in-country switches and extensions, the Global Business Mobility routes (Senior or Specialist Worker, Graduate Trainee, UK Expansion Worker, Service Supplier, Secondment Worker), the Minister of Religion route, the International Sportsperson route, and the Scale-up route. Most worker routes other than out-of-country Skilled Worker entry use Undefined CoS.
How do I request a Defined CoS?
Log into the Sponsorship Management System as a Level 1 User, open the Defined CoS request form, and enter the role's job title, SOC 2020 occupation code, gross annual salary, weekly working hours, start and end dates, and confirmation that the role meets the skill threshold. The Home Office normally responds within one working day for straightforward requests. Once approved, the Defined CoS appears in your account and you can assign it to the named worker.
How many Undefined CoS does a sponsor get?
Every sponsor licence is granted an annual allocation of Undefined CoS, set when the licence is approved and renewed each year on 5 April. The default for a new licence is the number requested in the application that the Home Office considers reasonable. If you run out, a Level 1 User can apply through the SMS for an increase at any point in the year and the Home Office will assess whether to grant it.
Can a Defined CoS be used for someone already in the UK?
No. Defined CoS are only valid for applications made from outside the UK. If the worker is already in the UK on another visa and wants to switch into Skilled Worker, the sponsor must assign an Undefined CoS instead.
What happens if I assign the wrong type of CoS?
The worker's visa application will be refused. Assigning a Defined CoS to an in-country applicant, or an Undefined CoS to an out-of-country Skilled Worker applicant, makes the application invalid. The CoS is consumed, the worker pays the application fee for nothing, and the sponsor must request and assign a fresh CoS of the correct type. Errors of this kind also appear in compliance reviews and can affect the sponsor's rating.