Sponsors assign two kinds of Certificate of Sponsorship (CoS): defined and undefined. The difference matters most to Skilled Worker sponsors, and the guidance treats using the wrong one as serious. This guide sets out the rules from Part 2 of the sponsor guidance and the Skilled Worker guidance. It explains which type the rules call for in which situation; it does not decide that question for any particular worker.
The two types in one sentence each
A defined CoS is for a Skilled Worker applying for entry clearance (a visa) from outside the UK. An undefined CoS is for a Skilled Worker applying for permission to stay from inside the UK, and for workers on every other route, wherever they apply from (Part 2, S2.8; GOV.UK).
So the type depends on the route and on where the worker makes the application, not on their nationality.
Undefined certificates come from an allocation
Undefined certificates are assigned from the sponsor's annual allocation (S2.9). A new sponsor asks for an allocation in its licence application, giving reasons, and UKVI decides how many to grant (S2.17, S2.18). A Skilled Worker sponsor is asked specifically for the number of undefined certificates it needs in the first year (Part 1, L6.24).
If the allocation runs out, a sponsor can ask for more through the sponsorship management system (SMS). GOV.UK says a decision usually comes within 12 weeks, and a sponsor can pay for a decision within 5 working days (SK11.6; GOV.UK).
Defined certificates are applied for one at a time
There is no allocation of defined certificates. A sponsor applies for one each time it needs one (S2.10, SK12.3). It can ask for several in one application if the role details, including start date, occupation code, job description and salary, are identical on each (SK12.3).
A sponsor can apply for a defined CoS either when it has identified a worker for an eligible role, or when it has an eligible role and reasonably expects to sponsor someone not currently in the UK (SK12.1). Only a Level 1 User can apply, through the SMS (SK12.6). There is no extra fee beyond the standard CoS fee of £525 on the Worker routes (SK12.7, checked 3 Oct 2026).
The application asks for the same role information as an undefined CoS (SK12.8). The salary must genuinely reflect what will be paid and must meet the Skilled Worker salary requirements (SK12.10). Where no worker has been identified yet, the sponsor cannot rely on certain salary points options without giving a clear justification in the application (SK12.12, SK12.13).
Decision time
GOV.UK says defined CoS applications are usually approved within one working day, and may take longer if UKVI needs to make further checks. SK12.20 says a straightforward application is normally decided within one working day. If UKVI asks for more information and it is not sent in time, the application is rejected (SK12.22).
SK12.24 lists reasons UKVI will reject an application, including a job that does not meet the skill or salary requirements, an inappropriate occupation code, a role that is not genuine or amounts to hiring the worker out to a third party, a job that breaks UK employment law, and false or misleading information. Repeated rejections can lead to compliance action (SK12.27).
The 90-day and 3-month rules
Once a defined CoS appears in the SMS, the sponsor must assign it within 90 days or it is removed (SK12.28). The worker then has 3 months to use it in an application (SK12.29). The guidance advises applying for a defined CoS only when the sponsor genuinely intends to assign it within 90 days.
When assigning a defined CoS, the pre-filled details cannot be edited. A sponsor note can change only the salary (if it earns the same points), weekly hours (with a matching salary update) or the start and end dates. Any other change, such as a different occupation code or job description, must be reported so UKVI can cancel the CoS (SK12.32 to SK12.34).
Rating and suspension
A B-rated or suspended sponsor cannot apply for a defined CoS (SK12.4). SMS guide 1 confirms that B-rated Worker and Temporary Worker sponsors cannot apply for or assign defined certificates. Unassigned defined certificates held when a licence is downgraded or suspended cannot be assigned and are removed after 90 days, unless the A-rating is regained in time (SK12.30).
Getting it wrong
Part 2 (S2.11) and SK11.7 say a sponsor must not assign a defined CoS for any job other than the one described in its application, or an undefined CoS where a defined one is required. SK11.8 says that assigning the wrong type, or giving false information on a defined CoS application, is likely to lead to revocation. SK12.2 repeats this for undefined certificates assigned to workers applying from outside the UK.
Care worker codes
SK12.18 says sponsors can no longer apply for a defined CoS under occupation codes 6135 (care workers and home carers) or 6136 (senior care workers). Workers under these codes can be sponsored only if they are applying from inside the UK and the additional requirements for those codes are met. The role checker shows the published rules and notes for each code.
Common questions
Does the type depend on the worker's nationality?
No. It depends on the route and on whether the Skilled Worker applies from outside or inside the UK (S2.8).
Can we keep a stock of defined certificates?
No. There is no annual allocation of defined certificates, and each one must be assigned within 90 days of being granted (SK12.3, SK12.28).
Does a defined CoS cost more?
No. SK12.7 says there is no additional fee beyond the standard CoS fee. The Immigration Skills Charge may also apply; the cost calculator shows both.
Who in our organisation can apply for one?
Only a Level 1 User (SK12.6). The compliance checklist lists the duties that follow once a certificate is assigned.