A Certificate of Sponsorship (CoS) is the central document for Skilled Worker visas. it’s a digital record generated through the Sponsor Management System (SMS), not a paper certificate. Employers must enter precise job details (title, SOC code, duties), salary and hours, work location, start date, and personal information on the CoS. Accurate CoS details are essential for a smooth Skilled Worker visa process. Every CoS must be assigned in line with Skilled Worker Rules. This guide helps HR teams get every CoS field right, avoid common mistakes, and understand the process of requesting and assigning a CoS.
The CoS is essentially a digital record of the job offer that a sponsored worker uses in their visa application.
There are two types of CoS: Defined and Undefined.
Use a Defined CoS for a worker applying from outside the UK. You must first request a Defined CoS via the SMS and wait for UKVI approval.
Use an Undefined CoS for a worker already in the UK, (extending their current or switching visa). This is taken directly from your annual allocation in the SMS. It’s crucial not to mix these up. Assigning an Undefined CoS to someone abroad, or vice versa, is forbidden and can lead to licence revocation.
The SMS CoS form has mandatory fields. Listed below are the main categories and what to include.
On the CoS, enter the exact job title of the role, and select the correct SOC 2020 occupation code from the drop-down list. The SOC code determines the role’s minimum salary. Make sure to select the most fitting SoC code to the role as using the incorrect code for the duties is a common cause of refusal.
Check the official Skilled Occupations list or use the CASCOT tool to verify the SOC code matches the role’s typical duties. In the “Summary of job description” box, briefly describe the main duties to justify the chosen code.
Enter the actual gross salary and weekly hours. If the applicant is joining the Skilled Worker route after 4 April 2024, the salary must meet the higher of the general Skilled Worker threshold and the going rate for the SOC code (the general threshold is £41,700; new entrants, PhD holders, and Health & Care routes may have reduced thresholds – see Appendix Skilled Occupations). If the applicant had their first CoS assigned prior to 4 April 2024 and is extending their visa, then the lower general threshold (£31,300) and going rates apply. Only guaranteed base pay counts on the CoS, so exclude allowances, overtime, bonuses, tips or commission.
For more part-time roles, the going rate must be pro-rated by the hours specified on the CoS. Under the new rules effective April 2026, pay is also checked per pay period. The worker must be paid at least the required rate in each monthly. That means your payroll must pay the correct amount on time rather than allowing shortfalls or large increases later in the year.
The CoS must include the employer’s details. This includes the organisation’s name, address, and PAYE reference (if applicable). The main work address must also be entered on the CoS. If the worker will be at multiple locations, list the primary site plus any regular secondary addresses. If the sponsored worker will work at a third-party client site, you must fill in the “Summary of client contract” detailing the arrangement.
Double-check that the employer/trading names and addresses on the CoS match your Sponsor Licence details exactly. For client-site roles, have records of up-to-date master service agreements and statements of work on file in case of audit. Keep all workplace details up to date in SMS: if your address or ownership changes, report it immediately.
Enter the employment start date and intended end date on the CoS. The start date should be realistic, the worker cannot apply for a visa more than 3 months before this date. UKVI normally requires the CoS to be assigned within 3 months of use and the visa application to follow soon after. The maximum duration you can grant on a CoS is up to 5 years.
Common errors include choosing a start date that’s too early (before visas are likely processed) or too far in the future (making the CoS expire).
Even small mistakes on the CoS form can affect a visa application. Some of the most frequent errors include:
By double-checking each field and matching everything to official documents, most of these errors are easily avoided.
Whether you need a Defined CoS (for a new hire from abroad) or an Undefined CoS (for an in-UK switch or extension), all CoS work happens in the Sponsor Management System (SMS). Here’s a practical outline:
Correct CoS use is also a compliance duty. Once you assign a CoS to a worker, you must report if the worker fails to start, is absent over 10 days without permission, or if their job role changes. These are SMS reports under your sponsor obligations. Failing to do so, or entering false information on a CoS can be interpreted as non-compliance.
Record-keeping goes hand in hand with CoS accuracy. You must keep a clear file for each sponsored worker per Appendix D of the sponsor guidance. This includes copies of the CoS (showing job, salary, hours), the signed employment contract, payslips, recruitment evidence, passport, BRP/Home Office decision and proof of the worker’s qualifications if required. Inspectors will compare your SMS entries (CoS and reports) against these records. Any mismatch could trigger a compliance audit.
In short, CoS accuracy is the foundation of your ongoing sponsor compliance.
Q. How long is a CoS valid?
Once assigned, a CoS can be used by the worker for up to 3 months from the date of assignment. If it isn’t used in that window, it expires and a new CoS (with a new £525 fee) must be assigned. For Defined CoS (not yet assigned), you must assign it within 90 days of allocation, or it’s removed from your SMS.
QCan I correct an error on a CoS after assigning it?
Once a CoS is assigned, changing the route is not possible. You can cancel the CoS and reassign a new one if needed, but the original fee is lost. You can add a sponsor note to an assigned CoS to update salary or working hours for example – but the revised salary/hours must still meet the same criteria.
Q. How many CoS can I assign at once? There is no strict limit on simultaneous CoS as long as you have the allocation. You request Defined CoS as needed. For Undefined CoS, your licence allocates an allowance. If you run low, you must request more through SMS (annual allowances refresh automatically each year).
Q. What is the difference between defined and undefined CoS?
A Defined CoS is used only for workers applying from overseas; it must be approved by UKVI first. An Undefined CoS is for in-UK applications (extensions/switches) and comes from your licence’s normal allocation.
Q. Does the employer or worker pay the CoS fee?
The employer must pay the £525 CoS assignment fee; it cannot be charged to the employee (doing so risks licence revocation). Similarly, the Immigration Skills Charge is a sponsor cost and both must not be recouped from the sponsored worker.
Q. How does the SMS help with CoS compliance?
The SMS is the portal where you submit all CoS details and complete reporting duties. Every entry in SMS is treated as evidence of compliance. The Home Office can inspect it any time. It’s a live record of your sponsorship duties. Ensuring each CoS entry in SMS exactly matches your internal records (contracts, payroll, recruitment docs) is key.
A mistake-free CoS is the employer’s responsibility and the first step to a successful visa application. Taking time to verify every CoS field, from SOC code and salary to the worker’s name and start date pays off. A well-organised CoS means fewer requests from UKVI and a lower risk of UKVI audit.
For any uncertainties, professional advice from Migrate UK can help ensure your CoS details and processes are correct, avoiding delays or costly mistakes in the visa outcome.