How to Check if a Certificate of Sponsorship (CoS) is Genuine or Not

A Certificate of Sponsorship (CoS) is a crucial document in the UK’s immigration and employment process. But with rising visa fraud and fake documents circulating, verifying the authenticity of your CoS is more important than ever.

In this guide, we’ll walk you through how to check if a certificate of sponsorship is genuine, what red flags to look out for, how the system works behind the scenes, and what to do if you suspect something isn’t right.

What Is a Certificate of Sponsorship?

A CoS is an electronic document issued by a UK-licensed sponsor (usually an employer) to a migrant worker. It includes a unique reference number that the worker uses to apply for a skilled worker visa. CoS documents are not printed or signed—they exist only in the Home Office system and are issued through the sponsor management system.

There are two types:

• Defined CoS – for applicants outside the UK
• Undefined CoS – for applicants switching visa status from inside the UK

Learn more about the differences in our guide to Defined & Undefined Certificates of Sponsorship.

Each CoS acts as confirmation that a licensed sponsor has offered you a genuine job that meets the eligibility criteria for sponsorship. It includes your job title, salary, SOC code, and start/end dates. It also includes your personal details and a sponsor reference number that you will use during your visa application.

Why It’s Important to Verify a CoS

Using a fake or invalid CoS can:

• Lead to visa refusal or cancellation
• Trigger immigration bans or deportation
• Harm your employment record and future sponsorship prospects
• Damage the sponsor’s licence and reputation

Unfortunately, some applicants fall victim to fraud by fake agents or bogus employers. Others simply receive incorrect or outdated documentation from poorly managed sponsors. Either way, verifying your CoS protects your future in the UK.

How to Check if a CoS Is Genuine

1. Verify the Sponsor Licence

Start by confirming that your employer holds a valid sponsor licence. Search for their name on the official Home Office Register of Licensed Sponsors.

Check for the following:

• The business name and address match your job offer
• The sponsor licence is active (not suspended or revoked)
• The sponsor has the correct licence type (e.g. Skilled Worker)

If you can’t find your employer on the register, do not proceed with the job or visa application until you clarify their licensing status.

2. Check the CoS Number Format

Every CoS comes with an 11-character reference number starting with the letter "C". Example: C12345678901.

This number is used during the visa application. If it seems unusually short, long, or formatted incorrectly, it could be fake.

Employers should provide you with this reference directly via official email or in your offer letter.

3. Confirm Assignment and Expiry Dates

Each CoS includes:

• An assignment date
• An expiry date (usually within 3 months of assignment)
• Employment start and end dates

A valid CoS must be assigned recently and remain valid when you apply. If your expiry date has passed, or the dates don’t match the job offer, request clarification.

Learn more about timelines in our guide to how long does a sponsor licence take.

4. Cross-Check Job Details

You should carefully compare the job details on your CoS with what you were offered:

• Job title: Must match the job role offered
• SOC code: Should align with the UKVI’s official list of sponsored occupations
• Salary: Should meet the minimum threshold for the SOC code (or new entrant if applicable)

Refer to the Skilled Worker: eligible occupations and going rates or use our Minimum Salary Calculator.

5. Review Personal Information

Your CoS must accurately include:

• Full legal name
• Passport number
• Date of birth
• Nationality

Any errors or mismatches should be flagged to the sponsor. These must be corrected before submitting your visa application.

6. Check CoS Status

Ask your employer if the CoS has been "Assigned" in the SMS.

A CoS can be:

• Created: Drafted but not assigned to a worker
• Assigned: Officially issued and ready for visa application
• Used: Already applied with
• Withdrawn or Cancelled: No longer valid

Only "Assigned" CoS can be used to apply for a visa.

7. Look for Missing Key Details

Common warning signs of a fake CoS include:

• No PAYE reference number listed
• No SOC code or incorrect job code
• Salary listed too low or marked as "new entrant" incorrectly
• References outdated policies (e.g. shortage occupation discounts no longer in use)
• Expiry date is under 3 months from assignment date

8. Contact the Sponsor

If you’re ever unsure, contact your sponsor directly. Ask:

• When was my CoS assigned?
• Can you confirm the CoS number from your SMS?
• Has it been used before?

A genuine employer will be transparent and happy to help. If they can’t confirm the details or avoid your questions, consider seeking legal advice.

Behind the Scenes: How Employers Issue a CoS

Employers issue CoS through the Sponsor Management System. Only registered sponsors with a valid sms level 1 user can assign CoS to eligible migrant workers.

They must:

• Verify that the job meets salary and skill thresholds
• Enter all relevant job and personal details
• Pay a CoS assignment fee (check our visa fees calculator)
• Assign it within the SMS

If a CoS is incorrect, outdated, or not assigned properly, the worker's skilled worker visa application could be refused.

Still Not Sure? Get Help from Borderless

At Borderless, we help migrants, HR teams, and employers verify their sponsorships. Whether you’re applying for a visa, hiring from overseas, or unsure about your CoS, our immigration team can support you.

Get in touch to book a free consultation or run a CoS check.

Final Thoughts

A genuine certificate of sponsorship is essential for your UK work visa. Don’t take risks with fake offers or unofficial documents.

Use this guide to:

• Understand how the sponsor management system works
• Check your employer’s licence
• Match job and personal details accurately

And if you're still unsure, we're here to help.

Want more guidance? Explore:

• Sponsor Licence Application
• Sponsor Licence Compliance
• Sponsor Licence Revocation
• Certificate of Sponsorship Cost
• Immigration Skills Charge

Stay safe, stay informed, and make your UK immigration journey a smooth one.