The key distinction is both the immigration route and where the worker is applying from. A Defined Certificate of Sponsorship is required for a Skilled Worker applying for entry clearance from outside the UK. An Undefined CoS is used for a Skilled Worker applying from inside the UK and for workers on other sponsored routes, whether they apply from inside or outside the UK.
Using the wrong type can create serious problems. Home Office sponsor guidance says assigning an Undefined CoS where a Defined one is required can lead to sponsor compliance action, including licence revocation. The detail is covered in Certificates of Sponsorship.
Defined and undefined side by side
| Feature | Defined CoS | Undefined CoS |
|---|---|---|
| Who it is for | Skilled Worker applicants applying from outside the UK | Skilled Workers applying inside the UK and workers on other sponsored routes |
| How you get it | Requested individually through the SMS | Assigned from your annual allocation |
| Typical timing | Usually approved within 1 working day; longer if checks are needed | Immediate if allocation is available; extra allocation requests normally take up to 12 weeks |
| Validity once assigned | Must normally be used within 3 months | Must normally be used within 3 months |
| Skilled Worker CoS fee | £525 | £525 |
| If more are needed | Submit another Defined CoS request | Request an allocation increase |
Temporary Worker CoS currently cost £55, so the fee depends on the sponsorship route rather than simply whether the certificate is defined or undefined.
Planning your annual allocation
Your CoS year does not always run from 6 April to 5 April. That timetable mainly applies to certain sponsors whose allocation renewal was automated after the previous Tier 2 system. For many other sponsors, the allocation year runs for 12 months from the licence grant or the latest manual allocation renewal.
Eligible A-rated sponsors can receive automatic annual allocations. Where this applies, the new allocation is generally based on the number of certificates assigned during the previous CoS year. Unused allocation does not simply carry forward.
If automatic renewal does not apply, a renewal request can be submitted up to three months before the allocation expires. You can also request an increase during the allocation year. Standard additional-allocation requests usually receive a decision within 12 weeks, although an eligible priority request can provide a decision within five working days.
Planning realistic recruitment numbers therefore matters. Review projected hires, likely extensions and in-country switches before the allocation becomes urgent.
Getting the content right
A CoS records important details about the sponsored role, including job title, occupation code, salary, working hours, employment dates and work location.
The occupation code should reflect the actual duties. Read SOC codes and job descriptions alongside Skilled Worker sponsorship salary rules and check whether any relevant provisions under the Immigration Salary List apply.
Material errors can require the certificate to be withdrawn and a new one assigned. Minor mistakes may sometimes be corrected through a sponsor note, but the Home Office specifically identifies matters such as an incorrect occupation code or wrong route as significant errors.
Salary records also need to remain consistent after sponsorship begins. The implications of the April 2026 changes are covered in new Skilled Worker pay period rules.
If a worker is based across several offices, client premises or at home, make sure the recorded arrangements reflect reality. Our guide to multi-site and hybrid working explains when location changes should be reported.
Avoiding delays
Assign the certificate when the candidate is genuinely ready to apply. Once assigned, a CoS must normally be used within three months, and the worker must not submit their visa application more than three months before the employment start date.
Sponsors must maintain at least one eligible Level 1 User. Having more than one suitable user can improve resilience during holidays or staff departures, as explained in key personnel on a sponsor licence.
For Skilled Worker sponsorship, the Immigration Skills Charge is currently £480 for the first 12 months for a small or charitable sponsor and £1,320 for a medium or large sponsor, with further charges for additional six-month periods. Budget using the sponsor licence costs guide.
Your wider obligations are covered in sponsor duties and compliance and sponsor licence management best practice.
If you are not yet licensed, start with a sponsor licence application. Certificates underpin each sponsored Skilled Worker visa application, including genuine structures commonly described as self sponsorship. Skilled Worker permission can lead to settlement under its own qualifying rules, while some individuals may alternatively qualify for ILR based on long residence. Current requirements are available on the GOV.UK sponsorship pages.
Frequently asked questions
Can a defined CoS be used for someone in the UK?
A Skilled Worker applying for permission to stay from inside the UK should normally be assigned an Undefined CoS.
How long does an allocation increase take?
UKVI says additional Undefined CoS requests usually receive a decision within 12 weeks. Eligible sponsors may be able to use the paid priority service for a decision within five working days.
What if a candidate withdraws after assignment?
If the CoS has not been used in an immigration application, the sponsor can withdraw it through the SMS. The £525 CoS assignment fee is not refunded and the certificate is not returned to the allocation.
If your allocation is running low or your sponsorship records need reviewing, speak to Garth Coates immigration solicitors before a planned hire is delayed.
