Certificates of Sponsorship explained: defined and undefined, costs, allocation and start dates
What a Certificate of Sponsorship is, when you need a defined or an undefined one, what it costs, how your annual allocation works, what must go on it, and what to do when a worker cannot start within 28 days.
Published 22 October 2026 · 4 min read
Checked against official guidance on 22 October 2026. This post reflects GOV.UK: Sponsor guidance part 2, sponsor a worker, sections S2 and S3 (version 10/26, published 8 October 2026). Guidance changes, so check the linked pages for the current version. This is information, not legal advice.
What a Certificate is
A Certificate of Sponsorship (CoS) is not a paper certificate. It is an electronic record you create in the Sponsor Management System, with a unique reference number the worker uses in their visa application. It is your statement to the Home Office about the job: what it is, where it is, how many hours, what it pays and when it starts. Everything you do afterwards is measured against it, so treat it as the most important document in the worker's file.
Defined or undefined
There are two types (S2.8):
- A defined Certificate is for a Skilled Worker applying for entry clearance from outside the UK. You apply for each one individually through the SMS. GOV.UK says most are decided within one working day, though extra checks can take longer.
- An undefined Certificate is for a Skilled Worker applying from inside the UK, for example switching from the Graduate route or extending, and for workers on all other routes. These come from your annual allocation.
Your annual allocation
When your licence is granted the Home Office sets an allocation of undefined Certificates for your first Certificate year. Each Certificate year lasts 12 months, and unused Certificates do not carry over (S2.23). If you are A-rated and your allocation is active, it can renew automatically; otherwise you request a new allocation up to 3 months before the year ends (S2.26, S2.29).
If you need more during the year, request them through the SMS with a business case. GOV.UK says this usually takes up to 12 weeks, with a paid priority option that aims for 5 working days. Plan hiring with that delay in mind.
What it costs
The Certificate fee is £525 for Worker routes, including Skilled Worker, and £55 for Temporary Worker routes. For Skilled Workers you usually also pay the Immigration Skills Charge at the same time. You must pay these yourself. You cannot recover the Certificate fee or related administrative costs from a Skilled Worker assigned a Certificate on or after 31 December 2024 (S2.13).
What goes on it
Section S3.8 lists the information: the route, the worker's personal details, every work address, weekly hours, job title and a job description, start and end dates, salary, the occupation code, details of any agent you used, and route-specific information such as an ATAS certificate where needed.
Three fields cause most later problems:
- The occupation code. It must match the real duties of the job, not the nearest-sounding title. A code that does not fit the duties is a mandatory revocation ground.
- The job description. Write what the person will actually do, in enough detail that a compliance officer could compare it with their working day.
- The work addresses. List every site they will normally work at. A move to an unlisted site is a reportable change.
Timing
The worker must use the Certificate in a visa application within 3 months of you assigning it, and cannot apply more than 3 months before the start date on it. Assign it when they are ready to apply, not months in advance.
For extensions, the guidance recommends a start date of the day after their current permission ends (S3.11).
When the worker cannot start on time
The worker should normally start within 28 days of the latest of three dates: the start date on the Certificate, the date their visa says it is valid from, or the date they were told their visa was granted (S3.15). A delay of up to 28 days needs no report.
If it will be longer, you must either give the Home Office the new start date and the reason, or stop sponsoring them, and report it within 10 working days after the 28-day window ends (S3.16 to S3.17). Acceptable reasons include travel disruption, serving a contractual notice period with a current employer, waiting for an exit visa, and illness or bereavement (S3.19). The list is not exhaustive, but the reason must be genuine and you should keep evidence of it.
If a worker wants to go elsewhere
If a worker decides to take a job with a different sponsor before using your Certificate, they must ask you in writing to withdraw it. You then have 5 working days to do so (S6.15 to S6.16). Do not sit on the request; it can block their application elsewhere.
How Zetta HR helps
Zetta HR stores each worker's Certificate reference, occupation code, job title, salary, hours, start date and work site, and compares every later change against them. Its pre-change check warns you before you save a change that differs from the Certificate.
Assigning Certificates is done in the SMS. Zetta HR does not create or submit Certificates.
Sources
More guides
A Home Office compliance visit: what happens, what officers check, and how to prepare
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