The certificate is not a physical document. Instead, it is an electronic record with a reference number that the worker must provide when applying for entry clearance, permission to enter, or permission to stay in the UK. Without a valid CoS, a visa application under routes such as the Skilled Worker visa will fail.
The CoS exists solely to enable a worker's visa application. The worker must have a valid CoS before they can make a successful application, according to Home Office sponsor guidance.
What a Certificate of Sponsorship contains
Each CoS includes detailed information about the sponsored job, the employer, and the worker. The Sponsorship Management System requires sponsors to enter:
The worker's personal details (name, date of birth, nationality, passport number)
Job title and description
Standard Occupational Classification (SOC) code
Annual salary or hourly rate and guaranteed working hours
Start and end dates of employment (for temporary roles)
Details of any allowances included in the salary
Confirmation that the role meets skill and salary requirements
The information entered by the sponsor is checked by Home Office caseworkers when the worker submits their visa application. Any discrepancies can lead to a refusal, so accuracy is essential.
Types of Certificate of Sponsorship
There are two types of CoS: defined and undefined.
Defined Certificate of Sponsorship
A defined CoS is used when the worker is outside the UK and applying for entry clearance to come to the UK for the first time, or when they are applying from outside the UK to return. Sponsors must request an allocation of defined CoS certificates from the Home Office, according to sponsor guidance. The Home Office sets annual limits on the number of defined CoS available to each sponsor, though employers can request additional allocations if required.
Defined CoS are typically used for:
Workers applying from abroad for their first UK work visa
Workers who have left the UK and are re-applying for entry clearance
Roles filled through international recruitment campaigns
Undefined Certificate of Sponsorship
An undefined CoS is used when the worker is already in the UK and is either switching from another visa category to a sponsored route, or extending their existing sponsored visa with the same or a new employer. Sponsors do not need to request an allocation for undefined CoS; they can assign them directly via the Sponsorship Management System as long as the sponsor licence remains valid.
Undefined CoS are typically used for:
Workers switching to a Skilled Worker visa from routes such as the Graduate visa or Student visa
Workers extending their existing Skilled Worker visa with the same employer
Workers changing employer within the UK while holding a Skilled Worker visa
How employers assign a Certificate of Sponsorship
Only licensed sponsors can assign a CoS. Employers must first apply for a sponsor licence and be approved by the Home Office. The process involves demonstrating that the organisation is genuine, operating lawfully in the UK, and capable of meeting sponsor duties.
Once licensed, the sponsor assigns a CoS via the Sponsorship Management System by:
Logging into the online system with authorised user credentials
Selecting the appropriate worker route (e.g. Skilled Worker)
Entering the worker's personal and job details
Confirming that the job meets eligibility criteria (skill level, salary, SOC code)
Assigning the CoS and providing the reference number to the worker
The CoS reference number is typically 16 characters long and must be entered by the worker when completing their visa application online.
If the worker does not meet the usual salary requirements and does not work in healthcare or education, they might still be eligible if their salary will be at least £33,400 per year.
For workers in health and care occupations, or those qualifying under transitional provisions, the minimum salary may be £29,000 per year, provided the worker is paid the going rate for the occupation code.
Pro-rata salary calculations
Part-time workers can be sponsored, but the salary must be pro-rated to reflect the guaranteed hours. The Home Office guidance specifies that sponsors must calculate the pro-rated salary based on the worker's guaranteed weekly hours compared to the standard full-time equivalent (usually 37.5 or 40 hours).
For example, if a role has a full-time salary of £45,000 for 37.5 hours per week, and the worker will work 30 hours per week, the pro-rated salary is:
(30 ÷ 37.5) × £45,000 = £36,000
The sponsor must enter the pro-rated salary on the CoS, and it must still meet the relevant minimum threshold.
Costs and fees for employers
Employers pay a fee to assign a CoS. The allocation fee applies to defined CoS only; undefined CoS do not incur an allocation fee, according to UK visa sponsorship guidance.
In addition to the CoS allocation fee, sponsors must also pay the Immigration Skills Charge for most workers. The charge is:
£1,000 per year for large sponsors
£364 per year for small sponsors or charitable sponsors
The charge is paid when the CoS is assigned and covers the duration of the visa being applied for, up to a maximum of five years, as set out in sponsor guidance.
Certain roles are exempt from the Immigration Skills Charge, including:
PhD-level occupations (SOC codes beginning with 211 or 212)
Jobs in healthcare and education under specific SOC codes
Workers switching from the Student visa route under certain circumstances
Validity and expiry of a Certificate of Sponsorship
A defined CoS is valid for three months from the date it is assigned. The worker must submit their visa application within this three-month window, according to Home Office guidance. If the worker does not apply in time, the CoS expires and the sponsor must assign a new one.
An undefined CoS does not have a fixed expiry date in the same way, but the worker must still apply for their visa before their current permission expires.
Once assigned, a CoS cannot be edited. If the sponsor enters incorrect information, they must withdraw the CoS and assign a new one. Withdrawing a CoS does not refund any fees paid.
Common reasons a CoS may be refused or withdrawn
The Home Office may refuse to grant a sponsor the allocation of defined CoS if:
The sponsor has breached their licence duties
The sponsor's licence is under review or has been downgraded
The requested allocation exceeds the sponsor's track record of compliance
A sponsor may also voluntarily withdraw a CoS if:
The worker declines the job offer
The job offer is withdrawn
Incorrect information was entered on the CoS
The worker's circumstances change before they apply for the visa
If a CoS is withdrawn before the worker applies, the sponsor may request a refund of the Immigration Skills Charge, but the CoS allocation fee is not refundable.
Rules that changed in April 2026
The Sponsor a Skilled Worker guidance version 04/26 reflects changes to Immigration Rules set out in Statement of Changes HC 1691, published 5 March 2026. These changes apply to Certificates of Sponsorship assigned on or after 8 April 2026.
Key changes include updated salary thresholds and clarifications to transitional provisions for workers already in the UK. Sponsors assigning CoS from 8 April 2026 onward must apply the updated rules, even if the worker was previously sponsored under earlier rules.
Employer duties after assigning a Certificate of Sponsorship
Assigning a CoS creates ongoing compliance obligations. Sponsors must:
Ensure the worker starts the job described on the CoS within the timescales allowed
Report any significant changes to the worker's employment (e.g. salary reduction, absence, early termination) via the Sponsorship Management System within 10 working days
Keep records of right-to-work checks, employment contracts, and payroll evidence
Cooperate with Home Office compliance visits and audits
Failure to meet these duties can result in the sponsor licence being downgraded, suspended, or revoked.
What happens if a worker's visa is refused
If the worker's visa application is refused, the CoS becomes invalid and cannot be reused. The sponsor may assign a new CoS if the worker is eligible to reapply and the refusal was due to an administrative error or missing documentation.
If the refusal was due to the job not meeting eligibility requirements, the sponsor must address the underlying issue (e.g. correct the SOC code, increase the salary) before assigning a new CoS.
The Immigration Skills Charge is not refundable if the visa is refused, according to sponsor guidance.
Record-keeping and audit requirements
Sponsors must retain evidence to support every CoS assigned. Required records include:
Copy of the worker's passport and right-to-work documents
Employment contract signed by both parties
Job advertisement and recruitment records (if applicable)
Evidence that the salary meets the minimum threshold and going rate
Payroll records showing actual salary paid
Records of any allowances claimed as part of the salary
The Home Office may request these records during a compliance audit or if a worker's visa application is selected for additional scrutiny.
Checking a Certificate of Sponsorship reference number
Workers should verify the details on their CoS before submitting their visa application. The worker cannot access the full CoS record in the Sponsorship Management System, but the sponsor should provide them with a summary of the information entered, including:
CoS reference number
Job title and SOC code
Salary and working hours
Start date of employment
Sponsor licence number
The worker must enter the CoS reference number exactly as provided when completing their visa application online. Any mismatch will cause the application to fail.
Support and guidance for sponsors
The Home Office publishes detailed guidance for sponsors in the Workers and Temporary Workers route. Sponsors can also contact UK Visas and Immigration for technical support with the Sponsorship Management System.
For complex cases or queries about eligibility, sponsors may seek advice from immigration lawyers or professional advisors, but all sponsor duties and compliance obligations remain the responsibility of the licensed organisation.
