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A genuine Certificate of Sponsorship comes with a unique reference number tied to a real, active sponsor licence — a worker offered “sponsorship” with no CoS reference, or asked to pay for one, should treat that as a serious warning sign.
What a genuine Certificate of Sponsorship actually records
A CoS isn't a physical document handed over on the first day — it's an electronic record the sponsor creates and assigns through the Home Office's sponsorship management system, and it holds specific fields that should match reality exactly:
- The unique CoS reference number itself.
- The sponsoring organisation's name and licence details.
- The job title and the occupation code it's assigned under.
- The salary the role will actually pay.
- The intended start date, along with the application details it's tied to.
A worker is entitled to see the details relating to their own sponsorship, and a mismatch between what's recorded and what they're actually being offered — a lower salary once they start, a different job title, duties that don't match the occupation code — is worth raising before accepting the role, not after.
Warning signs for workers
Being asked to pay for a Certificate of Sponsorship, being promised one before any role or salary details are confirmed, or being unable to verify the sponsoring organisation on the public register are all signs worth pausing on — see our guide on visa scam investigations for the fuller picture.
Warning signs for employers reviewing a candidate's history
A candidate who's held multiple short sponsorships in quick succession, or whose previous CoS details don't reconcile with what they describe, is worth a closer look before you assign a new one — not as an accusation, but as due diligence.
Legitimate reasons for multiple sponsorships versus a genuine red flag
Not every candidate with more than one CoS on their immigration history is a concern — genuine career moves, a fixed-term contract ending naturally, or an in-country switch from a different visa route onto sponsorship all produce a normal-looking pattern of more than one certificate over time. What's worth a closer look is a pattern that doesn't add up on its own terms: sponsorships that end abruptly well before a fixed term should, employers on the history that can't be found on the current register, or a timeline where the dates the candidate describes don't match what's on record. Ask for an explanation before assuming the worst, but don't skip the register check just because the explanation sounds plausible.
A Certificate of Sponsorship isn't valid indefinitely
Beyond the reference number and the details it records, a CoS also carries a defined window within which the visa application it supports has to be submitted — check the current validity period on GOV.UK rather than assuming an older certificate is still usable. An expired, unused CoS doesn't extend or roll over automatically; if a candidate's start date has slipped for any reason, the sponsor needs to assign a fresh certificate rather than relying on one that's run past its window, and a worker relying on an expired reference to apply is likely to have that application rejected outright.
Cross-checking the CoS against the actual job, not just the paperwork
Beyond confirming the sponsoring organisation is genuinely licensed, it's worth checking that the salary recorded on the CoS actually clears the relevant threshold for the occupation — our guides on the salary floor and going rates by occupation explain how that's calculated. For an employer, assigning a CoS with a salary or job title that doesn't genuinely reflect the role — even where there's no intent to deceive — creates the same compliance exposure as a knowing misrepresentation, because sponsor duty breaches are assessed on the accuracy of the record, not on whether carelessness or dishonesty caused the gap.
When a CoS reference has been reused or reissued
A CoS reference should correspond to one assignment, for one worker, for one application. A reference that's been reused across multiple candidates, or reissued repeatedly for the same person without a clear reason — a withdrawn application, a changed start date — is unusual enough to warrant a direct question to the sponsoring organisation, or a check against the register, rather than taking the explanation at face value.
How to actually verify a CoS
Cross-check the sponsoring organisation against the public register of licensed sponsors directly, rather than relying solely on documents provided by either party.
FAQ
Can a worker check their own CoS is genuine?
They can confirm the sponsoring organisation is on the public register — the CoS reference itself isn't independently publicly searchable, so employer transparency matters here.
What should a worker do if they suspect their CoS is fraudulent?
Report it — continuing to rely on a fraudulent CoS risks the worker's own status, regardless of who set the scheme up.
If an employer's CoS details turn out to be inaccurate, does that put the worker's status at risk?
It can — a visa granted on the basis of inaccurate sponsorship details can be curtailed even where the worker had no part in the inaccuracy, which is exactly why independent verification against the register, and a direct comparison with the actual job offer, matters as much for the worker as for the employer.
Related: Visa scam investigations · Checking a sponsor's licence status
GOV.UK references: Register of licensed sponsors
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