Certificates of Sponsorship (CoS): A Practical Guide for UK Employers

Certificates of Sponsorship (CoS) are a key part of the UK’s Points-Based Immigration System. They act as a digital link between UK sponsors and the overseas or in-country workers they wish to hire. If your organisation sponsors overseas workers through routes like the Skilled Worker visa or Global Business Mobility schemes, understanding how CoS works is essential.

At Imminova, we help employers manage this complex process, making sure each CoS is used correctly, complies with Home Office requirements, and supports your recruitment goals.

1️⃣ What is a Certificate of Sponsorship?

A Certificate of Sponsorship (CoS) is an electronic reference number issued by a licensed sponsor to a prospective worker. It shows the Home Office that the job offer meets the requirements of the relevant visa route. While not a physical document, the CoS plays a crucial role in any work visa application.

Each CoS must be linked to a genuine vacancy. Mistakes or misuse can lead to delays, visa refusals, or even penalties for the employer.

2️⃣ Defined vs Undefined CoS

There are two types of CoS:

Defined CoS

• For Skilled Worker visa applicants outside the UK

• Must be requested through the Sponsor Management System (SMS)

• Processing time: usually 1 working day

• Cannot be assigned until approved by the Home Office

Undefined CoS

• For:

  • Workers already in the UK (e.g. switching or extending visas)

  • Certain visa routes like Global Business Mobility

• Sponsors receive an annual allocation of these

• Can be assigned directly, provided you have remaining allocation

3️⃣ How to Request a CoS

Defined CoS:

1. Log into the Sponsor Management System

2. Select "Defined CoS Requests"

3. Enter job title, occupation code, salary, location, and any relevant tradeable points (e.g. shortage occupation)

4. Submit and wait for approval (typically 1 working day)

Note: You may need to submit supporting documents, especially for care or high-risk roles.

Undefined CoS:

• Request your allocation when applying for or renewing your sponsor licence

• If you run out during the year:

  1. Submit a request for more Undefined CoS

  2. Include a business justification

  3. Wait up to 18 weeks (faster if priority processing is available)

4️⃣ Which Visas Require a CoS?

CoS is required for the following routes:

• Skilled Worker

• Scale-up

• Global Business Mobility

• International Sportsperson

• Temporary Worker categories

CoS Fees:

Visa Type	Cost per CoS
Skilled Worker	£525
Temporary Worker	£55
International Sportsperson (12+ months)	£525
International Sportsperson (≤12 months)	£55

5️⃣ Annual CoS Allocation

Sponsors are given an annual allocation of Undefined CoS, based on expected need. Most sponsors receive auto-renewal, but some (particularly older licences) still follow the April-to-April cycle.

Avoid delays by checking your allocation regularly and requesting increases well before you run out.

6️⃣ CoS for UK Expansion Workers

Sponsors under the UK Expansion Worker route:

• Start with 1 CoS for the Authorising Officer

• After the AO enters the UK and the licence is upgraded to A-rating, you can request 4 more CoS

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7️⃣ Increased Home Office Scrutiny

Sponsors must now provide more detail when requesting Defined CoS, especially in sensitive sectors. You may be asked for:

• Organisation chart

• Justification for the role

• Recruitment records

• Employment contracts

• Proof of registration (e.g. CQC for care providers)

This reflects the government's increased focus on compliance and genuine hiring practices.

8️⃣ Common Pitfalls to Avoid

❌ CoS expiry: Valid for 3 months. If unused, cancel and reissue.

❌ Wrong job code or salary: Can lead to refusal or licence issues.

❌ Missing paperwork: You must retain contracts, pay records, and job descriptions.

❌ Incorrect data: Job title, hours, and location must match what's on the CoS.

❌ Unused or misused CoS: Repeated misuse may flag you for audit.

❌ Immigration Skills Charge: Pay this upfront if required.

9️⃣ FAQs

What's the difference between Defined and Undefined CoS?

Defined: for applicants outside the UK.Undefined: for applicants inside the UK or other routes.

How long is a CoS valid?

3 months from the date it's assigned.

Can I reuse a CoS?

No. If it's unused, it must be cancelled.

Do I need to request Undefined CoS every time?

Only if your annual allocation runs out.

What if my request is refused?

You may reapply unless the refusal includes a formal restriction.

🔟 How imminova Can Help

At imminova, we work with SMEs and HR professionals to simplify CoS management.

Our platform and advisory team help you:

✅ Plan and request the right type of CoS

✅ Build evidence to reduce the risk of refusal

✅ Stay compliant with Home Office requirements

✅ Manage allocation levels and prepare for audits

📩 Need help with a CoS request or compliance issue? Contact us for support that’s designed for busy employers. Let us take care of the paperwork so you can focus on growing your team.