Assigning a Certificate of Sponsorship (CoS) can feel like a daunting task for many UK employers and HR managers. With strict Home Office regulations, the risk of compliance errors, and the responsibility of supporting skilled migrant workers, navigating the process can be challenging. In the article, our UK immigration solicitors break down the assignment of a CoS step by step, including the difference between Defined CoS and Undefined CoS, helping employers meet their obligations and streamline visa sponsorship.
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What is a Certificate of Sponsorship?
A Certificate of Sponsorship is a unique digital reference number issued by a licensed UK sponsor that allows a foreign worker to apply for a visa under the Skilled Worker route. It is not a physical document but an official record confirming that the worker has a legitimate job offer with a licensed sponsor.
Defined vs. Undefined CoS
It’s essential to understand the two types of CoS:
1. Defined CoS
- Issued to individuals outside the UK applying for a Skilled Worker visa for the first time.
- Employers must request a Defined CoS from the Home Office, which is subject to allocation limits. A decision should be made within 3 working days.
- Typically used for candidates joining the UK workforce from abroad.
2. Undefined CoS
- Can be assigned to current employees already in the UK who are switching employers or extending their visas.
- Employers do not need a quota allocation to assign an Undefined CoS.
- Ideal for internal transfers or visa extensions for skilled workers already in the UK.
Understanding which type of CoS to assign is critical to avoiding visa refusals and maintaining compliance with Home Office rules. Our expert at Colman Coyle is here to assist.
Who can be sponsored?
Eligible individuals typically fall under the Skilled Worker visa criteria:
- Skilled roles on the Home Office’s eligible occupations list
- Meeting the minimum salary threshold
- Holding the required qualifications and experience
Employers must ensure that each candidate meets these eligibility requirements before assigning a CoS, and they must also determine whether a Defined or Undefined CoS is appropriate.
Step-by-Step Guide to Assigning a Certificate of Sponsorship
1. Confirm Your Sponsor License
Ensure your company holds a valid Sponsor License. Without it, you cannot legally assign either type of CoS.
2. Check role and candidate Eligibility
Confirm the role qualifies under Home Office guidelines.
- Determine whether the candidate requires a Defined or Undefined CoS.
3. Allocate the Certificate of Sponsorship
- Defined CoS: Request from Home Office allocation and assign once approved.
- Undefined CoS: Assign directly via your Sponsor Management System (SMS) without allocation limits if you have availability.
- Record all job details accurately in the SMS.
4. Keep accurate records
Maintain detailed records for each sponsored worker, including CoS type, role, salary, and employment dates.
5. Communicate clearly with the candidate
Provide the candidate with their unique CoS reference number and explain their next steps for visa application. We advise a printout of the assigned CoS is given to the candidate.
Common Challenges and How to Overcome Them
- Quota limits for Defined CoS: Plan international hires carefully to ensure allocation availability.
- Incorrect CoS type: Assigning the wrong type can delay or invalidate a visa.
- Administrative errors: Small mistakes in the SMS can have serious consequences.
FAQs About Certificates of Sponsorship
Q1: What is the difference between Defined and Undefined CoS?
Defined CoS is for applicants outside the UK and is subject to allocation limits, while Undefined CoS is for current UK-based employees switching roles or extending visas and does not require allocation.
Q2: How long is a CoS valid?
Typically, valid for 3 months from the date of assignment for visa applications.
Q3: Can I assign a CoS to any foreign worker?
No. Only eligible candidates applying for skilled roles under your sponsor license can receive a CoS, and the correct type must be used.
Q3: What is the cost to assign a CoS?
The Employer must pay the CoS fee which £525 now and the Immigration Skills charge which is £364 for small organisation and £1000 for medium or large organisation. Each additional 6 months is £182 and £500 respectively.
Immigration skills charge (“ISC”)
The ISC must be paid by employers sponsoring skilled foreign workers and reinvested in training the domestic workforce, is being raised by 32% from 16 December 2025.
The table below shows the new fees as from 16 December 2025 once the Immigration Skills Charge (Amendment) Regulations 2025 (SI 2025/1078) is adopted in parliament.
| Period | Small or charitable sponsors | Medium or large sponsors |
| First 12 months | £480 | £1,320 |
| Each additional 6 months | £240 | £660 |
Conclusion
Assigning a Certificate of Sponsorship, whether Defined or Undefined can seem overwhelming. However, with careful planning, knowledge of CoS types, and adherence to Home Office guidance, UK employers and HR managers can confidently sponsor skilled workers, maintain compliance, and contribute to a productive workforce.
Speak to the Immigration Lawyers at Colman Coyle.
Our Immigration Lawyers Can Help You:
✅ Determine whether your business qualifies for a sponsorship licence
✅ Advise on the correct Certificate of Sponsorship
✅ Provide ongoing legal advice after approval to help you manage your sponsored workers
Why Choose Colman Coyle
- Over 10 years’ experience in UK immigration and business sponsorship law
- Proven success rate with SME sponsor licence approvals
- Transparent fixed-fee pricing and expert legal guidance
- Personal, tailored support from regulated immigration solicitors
Contact Our Immigration Lawyers today to get started.
