CoS Check UK: How to Check a Certificate of Sponsorship (2026)

Key Take aways for CoS number

A CoS number is always 11 characters starting with "C". Any deviation is a red flag worth querying before applying.
Workers cannot check CoS status in the SMS directly; only your sponsoring employer has SMS access.
A correctly formatted CoS number does not confirm the CoS is valid; status, expiry, and job details all need separate verification.
HR teams must ensure the CoS status is "Assigned" (not just Created) before sharing the number with the employee.
Errors in CoS details like wrong SOC code, salary mismatches, or personal data mistakes can cause visa refusals that delay start date of employee.

If you need to do a CoS check in the UK, confirming a Certificate of Sponsorship number is correctly formatted, assigned, and valid before a visa application, this guide walks HR teams and sponsored workers through every check.

What Is a CoS Number?

A Certificate of Sponsorship (CoS) number is an 11-character unique reference code beginning with the letter "C" for example, C12345678901. It is generated by a UK-licensed employer through the Home Office Sponsor Management System (SMS) once a CoS has been formally assigned to a worker.

This reference number is not on a physical document. The CoS exists entirely as a digital record within the Home Office system. Your employer shares the CoS number with you directly so you can enter it into your UK visa application.

CoS Check UK: How to Check a Certificate of Sponsorship

A full CoS check in the UK means confirming four things, not just the number:

Format: the number is 11 characters and starts with "C".
Status: the CoS shows "Assigned" (not Created, Used, Withdrawn or Cancelled) in the Sponsor Management System.
Details: job title, SOC code, salary and dates match the offer and meet UKVI thresholds.
Sponsor: the employer appears on the Home Office Register of Licensed Sponsors.

Workers can check the format themselves; only the sponsoring employer can check status in the SMS.

Why the CoS Number Matters for Your Visa Application

When sponsoring a worker under the UK Skilled Worker route, the Certificate of Sponsorship (CoS) number is the critical reference that connects the employee’s visa application to your organisation’s sponsorship record. UK Visas and Immigration (UKVI) uses this unique identifier to retrieve key assignment details from the Home Office system, including the job title, salary, SOC code, assignment start date, and CoS validity period.

If the CoS number is entered incorrectly, does not follow the required format, or has not yet been assigned to the worker, the visa application cannot be processed correctly. This can result in delays, requests for additional information, or even a visa refusal, regardless of whether all other supporting documents are in order.

How to Find Your CoS Number

Once a Certificate of Sponsorship (CoS) has been assigned, employers should ensure that the sponsored worker receives the correct CoS reference number. This information is typically shared through:

The employment contract or offer letter, where some employers include the assigned CoS reference.
An official communication from the HR, mobility, or immigration team responsible for managing sponsorship.
Supporting guidance provided to the employee during the visa application process, as the CoS reference must be entered into the relevant field of the UK Skilled Worker visa application.

Employers should communicate the CoS number directly to the sponsored worker and avoid relying on third parties to relay this information. If a CoS has been assigned but the employee has not received the reference number, the sponsoring organisation should provide it promptly to prevent delays in the visa application process.

How to Check a CoS Number Format Is Valid?

Before a sponsored worker submits their visa application, employers should verify that the assigned CoS number meets the following requirements:

CoS Number Format Checklist

Check	What to Verify	Red Flag
Length	Exactly 11 characters	Fewer than 11 or more than 11 characters
Starting Character	Begins with the letter "C"	Starts with any other letter or a number
Remaining Characters	Contains 10 numeric digits after the "C"	Letters, spaces, or special characters after "C"
Source	Provided directly by your employer	Shared by a third-party agent or through unofficial channels

Once you have your number, you should also learn how to verify a UK CoS is genuine to protect yourself from fraud.

How to Check if a UK Sponsor Is Licensed

Before relying on a CoS, confirm the employer is a licensed sponsor. Search the employer's name on the Home Office Register of Licensed Sponsors (published on GOV.UK). If the company isn't listed, or its rating shows an issue, treat the CoS as a red flag and query it before applying.

Can Employees Check CoS Status Directly Online?

No, the employees cannot check CoS status online as they cannot access the Sponsor Management System (SMS) directly. The SMS is an employer-facing portal, and only licensed sponsors with Level 1 SMS user access can view and manage CoS records.

Employers can help minimise visa delays and errors by ensuring that sponsored workers have accurate and complete Certificate of Sponsorship (CoS) information before they apply. Key checks include:

Confirming the CoS status in the Sponsor Management System (SMS). Only CoS records with an "Assigned" status can be used in a visa application.
Maintaining an active sponsor licence and ensuring compliance with Home Office sponsorship requirements.
Providing the worker with the key CoS details, including the job title, SOC code, salary, and assignment and expiry dates, so these can be cross-checked against the employment contract and visa application.

Proactively verifying these details helps ensure that the visa application accurately reflects the sponsorship record held by the Home Office, reducing the risk of processing delays or refusals.

What the CoS Number Does NOT Tell You

A correctly formatted CoS number confirms the reference exists but it does not confirm the CoS is valid, assigned, or free from errors. You still need to verify

The CoS status is "Assigned" (not Created, Used, Withdrawn, or Cancelled)
The expiry date has not passed (defined CoS expire within 3 months of assignment)
Personal details such as name, passport number, and date of birth are accurate
Salary and job details meet UKVI thresholds

For a full verification process, see our guide on UK CoS allocation and assignment.

Feature	Health and Care visa	Standard Skilled Worker visa
Application fee (up to 3 years)	£324	£819
Application fee (over 3 years)	£628	£1,618
Immigration Health Surcharge	£0 (exempt)	£1,035 per year
Immigration Skills Charge (employer)	Exempt	£480–£1,320 per year
General salary floor	£25,000 (national pay scale) / £31,300 (general)	£38,700
Standard processing	~3 weeks	~8 weeks
Route to settlement	5 years (currently)	5 years (currently)

What HR Teams Should Know About CoS Numbers

For HR managers and global mobility teams, issuing a CoS through the Sponsor Management System is the step that generates the CoS number. Before the number is available to share with the worker:

The CoS must be fully completed within the SMS with accurate job and personal detail.
It must be formally assigned not just saved as a draft.
The correct CoS type must be used: Defined CoS for overseas applicants, Undefined CoS for in-UK applicants.

Frequently Asked Questions : CoS Number UK

What format is a CoS number?

A CoS number is 11 characters long and always starts with the letter "C" followed by 10 digits — for example, C1234567890. If the reference you receive does not match this format, contact your employer immediately before submitting a visa application.

Can I check my CoS number status online as a worker?

No. Workers cannot access the Sponsor Management System (SMS). Only your sponsoring employer can view CoS status in the SMS. To confirm your CoS is assigned and valid, ask your HR team or immigration contact to check the status on your behalf.

Where do I enter my CoS number?

You enter your CoS number in the UK visa application form online when applying for a Skilled Worker visa or other sponsored work route. UKVI uses this number to retrieve your sponsorship details from the Home Office system to assess your application.

How long is a CoS number valid?

A Defined CoS (for applicants outside the UK) is valid for 3 months from the date of assignment. An Undefined CoS (for applicants switching status from inside the UK) also has a 3-month validity window. You must apply for your visa before the CoS expires or you will need a new one.

What happens if my CoS number is wrong in my visa application?

An incorrect CoS number will prevent UKVI from locating your sponsorship record, likely resulting in a visa refusal or a request for further information. Always double-check the number with your employer before submitting and ensure the CoS status is "Assigned" in the SMS.

Who provides the CoS number to the worker?

The sponsoring employer provides the CoS number directly, typically via an official email or in the offer letter. You should never rely on a third-party recruitment agent or unofficial source for this number — always request it directly from your employer’s HR or immigration team.

How do I do a CoS check in the UK?

A full CoS check in the UK means confirming four things, not just the reference number. First, check the format: a valid CoS number is 11 characters long and starts with the letter "C" followed by 10 digits. Second, check the status: only your sponsoring employer can log into the Sponsor Management System (SMS) to confirm the CoS shows "Assigned"; not Created, Used, Withdrawn, or Cancelled. Third, check the details: make sure the job title, SOC code, salary, and start and end dates match your offer and meet UKVI thresholds. Fourth, check the sponsor: search the employer's name on the Home Office Register of Licensed Sponsors to confirm they are authorised to sponsor workers. You can verify the format and the sponsor yourself, but only your employer can check the CoS status in the SMS.

Maliha Ahmed

Maliha Ahmed is an IAA-accredited Immigration Advisor at Jobbatical, specialising in UK business immigration. She holds an LLB Law (Honours) from Brunel University London and brings 8 years of experience advising SMEs and large enterprises on skilled worker visas, sponsor licence applications, Certificate of Sponsorship (CoS), SMS compliance, and global mobility. She is an active member of the Immigration Law Practitioners Association (ILPA) and she regularly participates in corporate immigration events to stay current with UKVI policy changes.

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