Employer Services

Certificate of Sponsorship (CoS)

A guide for UK employers on the two types of Certificate of Sponsorship, how to assign them correctly, and the Immigration Skills Charge.

Quick Overview

Certificate of Sponsorship (CoS) — Key Facts

A Certificate of Sponsorship is an electronic record — not a physical certificate — created through the Sponsorship Management System. Its reference number is a required component of every work visa application.

  • Electronic Record: A CoS is an electronic record in the Home Office SMS system — not a physical certificate.
  • Two Types: Defined CoS (for overseas applicants) and Undefined CoS (for in-country applications).
  • Valid for 3 Months: A CoS is valid for three months from the date it is assigned — the worker must apply within this window.
  • Immigration Skills Charge: £1,320/year for large sponsors, £480/year for small or charitable sponsors — paid when the CoS is assigned and cannot be recovered from the worker.
  • Accuracy Is Critical: The Home Office verifies CoS information during the visa application process — inaccuracies can cause refusal.
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In this article

What Is a Certificate of Sponsorship?

A Certificate of Sponsorship (CoS) is an electronic record created by a licensed sponsor through the Sponsorship Management System (SMS). It contains detailed information about the role, salary, sponsor, and period of engagement. The CoS reference number is a crucial component of any work visa application — the sponsored worker must include it in their Home Office visa application. Without a valid CoS, the worker cannot apply for their visa.

What Are the Two Types of CoS?

  • Defined CoS — Used for workers applying for a Skilled Worker visa from outside the UK, or switching from certain visa categories within the UK. Must be applied for individually and approved by the Home Office before being assigned.
  • Undefined CoS — Used for in-country applications under the Skilled Worker route and for Temporary Worker routes. Sponsors are allocated a pool of undefined CoS and can assign within their allocation without individual prior approval.

What Information Must Be Included on a CoS?

  • The sponsored worker's full name and personal details
  • The sponsor's licence number and organisation details
  • The job title and Standard Occupational Classification (SOC) code
  • The RQF level of the role
  • The gross annual salary (meeting the applicable threshold)
  • The start date and duration of employment
  • The work location or locations
  • Confirmation of whether the role is on the Immigration Salary List and any applicable salary concessions

How Long Is a CoS Valid?

A Certificate of Sponsorship is valid for three months from the date it is assigned. The sponsored worker must use the reference number to make their visa application within this window. If they fail to apply within three months, the CoS expires and a new one must be assigned. We recommend coordinating the CoS assignment closely with the worker's visa application timeline to avoid unnecessary delays or additional costs.

What Is the Immigration Skills Charge?

When a sponsor assigns a CoS for a Skilled Worker or Senior or Specialist Worker role, they must pay the Immigration Skills Charge (ISC) — a government levy to fund training for UK workers. The ISC is £1,320 per year (or part thereof) for medium and large sponsors and £480 per year for small or charitable sponsors. It is payable at the time the CoS is assigned and cannot be recovered from the sponsored worker under any circumstances.

Can a Certificate of Sponsorship Be Withdrawn?

Yes, before the worker uses it to make their visa application — for example if the job offer is withdrawn. Once a visa has been granted on the basis of a CoS, the sponsor cannot simply cancel it unilaterally. Instead, any change in the worker's employment must be reported through the SMS within the required timeframes.

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Common questions

Certificate of Sponsorship (CoS) FAQ

What is the difference between a Defined and Undefined CoS?
A Defined CoS is for overseas applicants and requires individual Home Office approval before assignment. An Undefined CoS is for in-country applications and can be assigned from the sponsor's pool without prior approval.
How long is a CoS valid?
Three months from the date it is assigned. If the worker doesn't apply within this window, a new CoS must be issued.
How much is the Immigration Skills Charge?
£1,320 per year for medium and large sponsors, or £480 per year for small or charitable sponsors. Paid when the CoS is assigned — cannot be passed to the worker.
What if information on the CoS is wrong?
Inaccuracies can cause visa refusal and create compliance issues for the sponsor. The Home Office verifies CoS information during the visa process. We review all details before assignment.
How many CoS can we assign?
The number of Undefined CoS available depends on your allocation. Defined CoS must be individually applied for and approved. We advise on managing your CoS allocation efficiently.
Can we assign a CoS before the worker has a visa?
Yes — in fact, the CoS must be assigned first. The worker uses the CoS reference number to make their visa application.
What happens if the CoS expires before the worker applies?
The CoS expires after three months. If the worker has not applied within this period, a new CoS must be assigned — which may incur an additional ISC payment.
Can the ISC be refunded if the worker leaves?
In some circumstances, a partial refund of the ISC may be available if the worker leaves the UK or their visa is curtailed within the period for which the charge was paid. We can advise on eligibility.
Quick Overview
Certificate of Sponsorship (CoS) — Key Facts

A Certificate of Sponsorship is an electronic record — not a physical certificate — that the sponsored worker needs to apply for their UK work visa. It is valid for three months from assignment.

  • Electronic Record Created in the Home Office SMS — not a physical document.
  • Two Types Defined (overseas, individual approval required) and Undefined (in-country, from pool).
  • Valid 3 Months Worker must apply for their visa within three months of assignment.
  • ISC Payable £1,320/year (large) or £480/year (small/charitable) — cannot be passed to the worker.
  • Accuracy Critical Inaccuracies can cause visa refusal — we verify all details before assignment.
Full article below ↓
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What Is a Certificate of Sponsorship?

An electronic record in the Home Office SMS containing details of the role, salary, sponsor, and engagement period. Its reference number is a required component of every work visa application.

Defined vs Undefined CoS

Defined CoS: for overseas applicants — individually applied for and approved by the Home Office before assignment. Undefined CoS: for in-country applications — assigned from the sponsor's pool without individual prior approval.

The Immigration Skills Charge

£1,320/year for medium and large sponsors; £480/year for small or charitable sponsors. Paid at the time of CoS assignment. Cannot be recovered from the sponsored worker.

Accuracy and the 3-Month Window

The CoS must be accurate — the Home Office verifies all information during the visa process. It is valid for three months; if the worker doesn't apply within this window, a new CoS (and potentially a new ISC payment) is required.

The accuracy of a Certificate of Sponsorship is critical. Even minor errors in job title, SOC code, salary, or start date can cause a visa refusal and a compliance issue for the sponsor. We review every CoS before it is assigned to ensure the information is correct and complete.

Assigning a Certificate of Sponsorship?
Get it right before you assign it.

We advise employers on the correct procedure for applying for and assigning Certificates of Sponsorship — checking role and salary compliance, verifying accuracy, and managing the timeline with the worker's visa application.

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Common questions

Certificate of Sponsorship (CoS) FAQ

A Defined CoS is for overseas applicants and requires individual Home Office approval before assignment. An Undefined CoS is for in-country applications and can be assigned from the sponsor's pool without prior approval.

Three months from the date it is assigned. If the worker doesn't apply within this window, a new CoS must be issued.

£1,320 per year for medium and large sponsors, or £480 per year for small or charitable sponsors. Paid when the CoS is assigned — cannot be passed to the worker.

Inaccuracies can cause visa refusal and create compliance issues for the sponsor. The Home Office verifies CoS information during the visa process. We review all details before assignment.

The number of Undefined CoS available depends on your allocation. Defined CoS must be individually applied for and approved. We advise on managing your CoS allocation efficiently.

Yes — in fact, the CoS must be assigned first. The worker uses the CoS reference number to make their visa application.

The CoS expires after three months. If the worker has not applied within this period, a new CoS must be assigned — which may incur an additional ISC payment.

In some circumstances, a partial refund of the ISC may be available if the worker leaves the UK or their visa is curtailed within the period for which the charge was paid. We can advise on eligibility.

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