What the CoS actually is
A Certificate of Sponsorship is a unique 8-character reference number (e.g. C2G7H9K3) generated in the Sponsor Management System (SMS), the Home Office's portal for licensed sponsors. When an employer decides to sponsor you, they assign one of their available CoS slots to your role and your personal details.
Once assigned, the CoS appears in your email from the employer and in the sponsor's SMS dashboard. You cannot see it on gov.uk directly. The CoS does not grant you the right to work — you use the CoS reference number in your visa application to prove you have a genuine UK job offer from a licensed sponsor.
What information a CoS contains
Every CoS contains the following fields: your full name and passport details, your date of birth, your nationality, the SOC 2020 occupation code, the job title, the sponsor employer details (licence number + trading name), start date, proposed end date, salary (and whether salary is "certified maintenance"), work location (site code), and hours per week.
A "restricted" CoS was historically required for out-of-country applicants, but since 2020 virtually all CoS are "defined" CoS — the same type whether you apply from inside or outside the UK. Employers apply for a defined CoS slot and typically receive it within 1 working day.
Details you must verify before applying
Before submitting your visa application, cross-check the CoS against your offer letter and employment contract. The salary on the CoS must match your contract exactly. The job title and SOC code should reflect your actual role — candidates are sometimes given a more senior-sounding title on the CoS than the contract, which becomes a refusal reason. The work location should match where you'll actually be based.
Verify that the salary meets both the £41,700 general threshold (or the lower applicable route) AND the going rate for the SOC code. Going rates are published on gov.uk per SOC code — if your salary is £42,000 but the going rate for the specific SOC is £48,000, you do not qualify. Our Salary Checker tool cross-references all three numbers in one click.
The 3-month CoS window
Once a CoS is assigned to you, you have 3 months to submit your visa application. After 3 months the CoS expires and cannot be reused. If your application is delayed (waiting on biometrics, translating documents, or finalising an English test), speak to your sponsor early — they can withdraw the expired CoS and issue a fresh one rather than force you to miss the window.
The start date on your CoS can be no more than 3 months after the date you're expected to enter the UK. If visa processing slips, employers sometimes need to amend the start date — this requires the sponsor to cancel and reissue the CoS with a new date, not simply edit the existing one.
Fees — who pays what
The CoS itself costs £525 (defined CoS, 2025 fee). Under Home Office rules in force since 2024, employers cannot pass this fee on to you — it must be borne by the sponsor. In addition, sponsors pay an Immigration Skills Charge per year of sponsorship: £1,000/year for large sponsors, £364/year for small sponsors. This too cannot be passed on to you. If an employer asks you to reimburse the CoS fee or Skills Charge, this is a red flag — report it to the Home Office.
You, however, pay the visa application fee (£719-£1,639 depending on duration), the Immigration Health Surcharge where applicable, the English language test, and biometric enrolment. These are entirely yours.
Common CoS-related refusal reasons
The top CoS-linked refusals we see: salary on CoS falls below the combined threshold + going rate; job title/SOC code mismatches the actual work described in the contract; CoS issued by an employer whose licence has been suspended or revoked (check our Sponsor Licence Checker before applying); expired CoS submitted with the visa application; or incorrect personal details (name spelling, passport number) on the CoS not matching your ID documents.
Before submitting your application, ask your sponsor for a PDF copy of the CoS details from their SMS export. Review every field. Five minutes of cross-checking can prevent a £1,639 refusal you cannot easily reverse.