Defined vs Undefined CoS: Which Certificate of Sponsorship Do You Need?
A defined certificate of sponsorship (CoS) is for a Skilled Worker applying for a visa from outside the UK. An undefined CoS is for a Skilled Worker applying from inside the UK and workers on all other sponsored work routes. The correct type depends on both the visa route and where the application will be made.
For employers and HR teams, the distinction affects how certificates are obtained, recruitment timing and sponsor compliance. This guide covers the comparison, practical examples, fees and mistakes to check before assignment.
Key Takeaways
- Defined CoS: For Skilled Worker applications made outside the UK.
- Undefined CoS: For in-country Skilled Worker applications and all other sponsored work routes.
- Format: Both are electronic records created through the Sponsorship Management System (SMS).
- Allocation: Undefined certificates use an annual allocation; defined certificates are requested as needed.
- Timing: Defined requests are usually approved within one working day; additional undefined allocations usually take up to 12 weeks.
- Fees: Both types cost £525 for Skilled Worker sponsorship. An undefined CoS for a GBM Graduate Trainee costs £55.
- Validity: Workers must use an assigned CoS for their visa application within 3 months.
- Compliance: Assigning an undefined CoS where a defined one is required may lead to licence revocation.
What is a certificate of sponsorship?
A CoS is an electronic record linking a sponsored worker to a specific job. A licensed sponsor assigns it through SMS and gives the worker a reference number for their visa application.
The sponsor must hold the appropriate licence and satisfy the relevant assignment requirements. A CoS does not guarantee visa approval or independently establish permission to work. Employers must still complete the required right to work checks.
If your organisation is not licensed, our Skilled Worker sponsor licence service explains the application support available.
What is the difference between defined and undefined CoS?
The main difference is the application process: defined certificates require a request for the proposed job, while undefined certificates are assigned from an approved allocation.
| Feature | Defined CoS | Undefined CoS |
|---|---|---|
| Applicants | Skilled Workers applying outside the UK | Skilled Workers applying inside the UK and all other sponsored work routes |
| How obtained | Requested through SMS as needed | Assigned from the sponsor's annual allocation |
| Annual allocation | None | Approved by the Home Office |
| Job details | Must match the approved request | Entered when the certificate is assigned |
| Skilled Worker fee | £525 | £525 |
These categories are not interchangeable. An available undefined certificate cannot be used simply because the employer wants to avoid waiting for a defined request.
The word "undefined" does not remove the need for a genuine, eligible role. Each certificate must still contain the required worker and job information when assigned.
Which CoS applies to your next hire?
Check the worker's intended route, application location and eligibility before choosing the certificate.
| Recruitment scenario | CoS type |
|---|---|
| Skilled Worker applying from overseas | Defined |
| Eligible Graduate or Student switching to Skilled Worker inside the UK | Undefined |
| Skilled Worker applying inside the UK to extend permission or change employer | Undefined |
| Global Business Mobility applicant, inside or outside the UK | Undefined |
| Temporary Worker applicant, inside or outside the UK | Undefined |
| Eligible care worker or senior care worker applying inside the UK | Undefined, with additional restrictions |
Being physically present in the UK does not automatically make someone eligible to switch routes. Care workers and senior care workers also face additional immigration-status and sponsorship conditions. Check the current Skilled Worker sponsor guidance before relying on an in-country application.
Our Temporary Worker sponsor licence service covers support for those routes.
How do you obtain each type of CoS?
Requesting a defined CoS
An authorised Level 1 user applies through SMS. Several certificates can be requested together where the required job details, including occupation code, duties, salary and start date, are the same.
GOV.UK says requests are usually approved within one working day, although additional checks can take longer. Once approved, the certificate appears in SMS for assignment to the worker.
Keep two deadlines separate:
1. Assign the defined CoS within 90 days of allocation to your SMS account.
2. The worker must use it for their visa application within 3 months of assignment.
Managing undefined CoS allocations
When applying for a sponsor licence, estimate and justify how many undefined certificates you need. The Home Office decides the allocation. Assignments then reduce your available balance.
Base your estimate on planned recruitment and existing workers' extension dates. Keep supporting information consistent with your staffing plans, and separate overseas Skilled Worker hires from hires that will use undefined certificates.
Unused certificates do not carry over into the next CoS year. Renewal arrangements vary by route and sponsor circumstances, so check your SMS allocation and renewal position before planning recruitment.
If you need more certificates, request an additional allocation through SMS. Decisions usually take up to 18 weeks. Eligible priority requests are normally considered within 5 working days, subject to availability and further checks. Priority is unavailable for UK Expansion Worker, Service Supplier and Secondment Worker requests.
How much does a certificate of sponsorship cost?
As of 27 October 2026, GOV.UK lists the following assignment fees:
- Worker routes: £525, except the shorter International Sportsperson category below.
- Temporary Worker routes: £55.
- International Sportsperson: £55 for sponsorship of 12 months or less; £525 for longer periods.
For Skilled Worker sponsorship, defined and undefined certificates have the same £525 fee. Sponsors are responsible for paying it.
For Skilled Worker, Global Business Mobility, Minister of Religion, International Sportsperson, Scale-up and Seasonal Worker sponsorship, current fee-recovery restrictions prohibit passing the CoS fee or associated administrative costs to the worker. Check route-specific guidance before arranging deductions or repayment clauses.
The Immigration Skills Charge may also apply to Skilled Worker and Senior or Specialist Worker sponsorship, subject to exemptions. This is separate from the CoS assignment fee.
Which CoS mistakes should employers avoid?
The Home Office sponsor guidance says licence revocation will normally follow if a sponsor assigns an undefined CoS where a defined one is required, or a defined CoS for a different job from the approved request.
Other checks matter too:
- Significant errors: A wrong occupation code or route requires withdrawal and a new CoS. Do not assume a sponsor note can correct every mistake.
- Application dates: The worker must apply within 3 months of assignment and cannot apply more than 3 months before the stated job start date.
- Allocation balance: Check available undefined certificates before agreeing a recruitment timetable.
- Eligibility: Confirm the worker and job meet the relevant route requirements before assignment.
Do not assume a certificate can be reused after a visa refusal. A fresh application normally requires a new CoS, subject to any administrative review outcome.
Use the sponsor licence compliance checklist to review wider record keeping and reporting duties.
How can MGBe Legal help?
MGBe Legal advises employers on sponsor licence applications and compliance. For CoS matters, support can include checking the appropriate certificate type, planning allocation requests and reviewing job details before assignment. Advice should reflect the employer's licence, the worker's circumstances and the proposed role.
Conclusion
Choose the certificate by route and application location, then check eligibility, allocation and deadlines. A short review before assignment can identify problems that would otherwise delay recruitment or affect sponsor compliance.
MGBe Legal can discuss your planned hires and the sponsorship steps they require.
Frequently Asked Questions (FAQs)
Gabriella Bettiga
Director of MGBe Legal
I founded MGBe Legal, a firm regulated by the Immigration Advice Authority (IAA), with the mission to provide high-quality, simplified, and accessible legal services to clients from all walks of life.
