Certificate of Sponsorship (CoS): A Practical Guide for UK Employers (2026)
A practical 2026 guide for UK employers on Certificates of Sponsorship (CoS), covering what they are, how to assign them, key compliance requirements, and common mistakes to avoid when sponsoring workers.
Dhruti Thakrar
Dhruti Thakrar is a leading UK immigration solicitor and partner at Keystone Law, with over 28 years of experience advising multinationals, blue-chip firms, startups, and high-net-worth individuals. Recognized by The Legal 500, she specializes in both corporate and personal immigration law, sponsor licence compliance, and complex casework.
The Certificate of Sponsorship (CoS) is a key part of the sponsorship process; however, it can feel complex and confusing due to the amount of detail needed to ensure a successful application. This guide aims to break down key steps in understanding a CoS, noting common mistakes and how to avoid them.
What is a Certificate of Sponsorship (CoS)?
A Certificate of Sponsorship is an electronic record that is assigned to foreign nationals enabling them to work in the UK under a specific visa. It consists of a unique number for each applicant that is entered when completing an online visa application. It contains the details of the job, such as the job title, salary, hours and start date, as well as personal details of the person it is assigned to. Knowing the procedure of how to apply and assign a CoS is important as mishandling of it can result in various repercussions, such as the employer’s sponsor license being downgraded, revoked or suspended. Furthermore, making a mistake during this application process can lead to the applicant having their visa refused by the Home Office.
If you have not yet secured a sponsor licence, start with our UK Sponsor Licence Guide.
Two Types of CoS: Defined and Undefined
There are two types of CoS that can be assigned: defined and undefined. Understanding the difference between the two allows for the correct type to be assigned in each circumstance. It is important to note that in December 2020, the Home Office changed the sponsorship system. Prior to this, CoS were referred to as ‘restricted’ and ‘unrestricted’.
Defined CoS
A defined CoS relates to individuals applying for a visa while they are overseas. An employer will need to apply through the online Sponsorship Management System (SMS). If the application is approved, it can then be provided to the overseas worker. The CoS must be assigned to a specific individual within three months, otherwise it will expire.
Undefined CoS
An undefined CoS is needed when the individual is in and applying from the UK. Generally, this applies to those switching from a different visa, such as a student visa. Under this route, a sponsor will have an annual allocation either upfront during their license application or by way of the SMS annually.
How to assign a CoS through the Sponsor Management System (SMS)?
The various steps to assigning a CoS through SMS are highlighted below:
- Log into the SMS and navigate to ‘Workers’ where you will find ‘Create and Assign CoS’.
- Select the correct route (e.g. Skilled Worker) and category, if needed.
- Create the Certificate: a new single certificate can be created and the form must be completed in full with the relevant information.
- For a defined CoS: first submit a request and wait for Home Office approval.
- For an undefined CoS: if allocation is available, proceed.
- Review all the details and confirm accuracy.
- Read the declaration and confirm all information is correct; select ‘Assign’ once complete.
- Payment is needed via Worldpay which includes the standard CoS fee and Immigration Skills Charge (ISC) if applicable.
- Once payment is processed, the CoS automatically updates to ‘Assigned’ and a unique CoS number is generated to share with the sponsored worker for their application.
What information must be included on a CoS?
When applying for, and assigning, a CoS various information is needed:
- Full name, date of birth and nationality of the applying worker
- Passport number
- Job title and description
- SOC code
- Salary (gross annual and hourly rate) and weekly contracted hours
- Employment start and end dates
- Work address(es)
- Sponsoring employer’s details
- Any additional tradeable points (e.g. PhD)
What are the salary and SOC code requirements at the point of assignment?
The SOC codes tend to cause error in applications; therefore, it is vital to ensure details regarding both the SOC codes and salary are in order. They determines eligibility for many visa routes and sets the going rate for eligible occupations. SOC codes are selected based on the job descriptions and job title to confirm the role qualifies for sponsorship.
Every SOC code has an associated going rate, which represents the typical minimum salary for that occupation in the UK labour market. For a successful application, the salary offered must satisfy the general salary threshold and the going rate for the appropriate SOC code.
The going rates are based on a 37.5-hour working week. It is important to note that if the contracted hours differ, they must be adjusted proportionally. In addition to this, it must be noted that the general salary threshold is calculated on up to 48 hours per week.
To confirm the job offer meets the relevant threshold, run the numbers through our free skilled worker salary calculator.
How long is a CoS valid and what happens if it expires?
Once the CoS has been assigned, the applicant has three months to submit their visa application. It is important to note, the three-month deadline begins from the date of assignment, not the employment start date. If the CoS expires, the employer must assign a brand new one. Therefore, in practice it is important to ensure the time of assignment coincides with when the worker is ready to apply and has all their documents in order.
What are the most common mistakes employers make when assigning a CoS?
To ensure the CoS application process is successful, there are some common mistakes than can be avoided. Such mistaken can include, assigning the wrong type of CoS – defined or undefined – or assigning the CoS before the applicant is ready, causing them to miss the three-month deadline. Furthermore, it is important to check Academic Technology Approval Scheme (ATAS) requirements, as some academic roles require an ATAS certificate before the CoS is assigned and paying the correct Immigration Sills Charge (ISC). Further mistakes are outlined below.
Mistakes on the CoS
Employers can make mistakes when entering details for the CoS, such as the salary, job title, start date or personal information for the prospective employee. If there is inconsistency between the CoS and the information provided by the individual in their visa application the entire process will take longer or result in the individual’s visa being rejected. Therefore, it is vital to double check each piece of information, especially relating to the salary and personal details of the potential employee.
Concerning salary, ensure that it meets the minimum threshold set out by the Home Office for that particular role. This can be complex with application where percentage reduction is relevant, therefore it is important to pay close attention to detail.
To confirm the worker qualifies for the CoS before assigning it, use our skilled worker visa eligbility check,
Incorrect SOC code
An incorrect SOC code, meaning one that does not match the skill level or responsibilities of the job on the application could lead to an individual’s visa being rejected. Reasoning would be based on the role offered not matching the criteria for sponsorship. To avoid this, rather than simply matching the job title, ensure the job duties are aligned.
What happens after the CoS is assigned?
Once the CoS is assigned, be sure to notify the worker immediately and share the unique CoS reference number generated. The worker needs this number to complete their online visa application with the relevant documents and details.
Processing times can differ based on the circumstances of the application. Current processing times can be viewed here: processing times.
Conclusion
Getting the Certificate of Sponsorship right is not just an admin step, it is the foundation of a successful visa application and ongoing compliance. Small mistakes can lead to delays, refusals, or even sponsor licence risks.
By following the steps in this guide, you can assign CoS with confidence, avoid common pitfalls, and keep your hiring process running smoothly.
If you are unsure about any part of the process or want a second pair of eyes before assigning a CoS, it is worth addressing it early. Fixing issues before submission is far easier than dealing with a refusal or compliance problem later.
If helpful, you can book a short consultation with our team to review your CoS before assignment and flag any risks upfront.