Answer · Certificate of Sponsorship

What is a Certificate of Sponsorship?

Direct answer

A Certificate of Sponsorship (CoS) is a unique reference number issued by a licensed UK sponsor through the Sponsorship Management System (SMS). It confirms that the sponsor has offered the worker a specific role on specific terms, and is what the worker uses to apply for their sponsored work visa. A CoS is not a physical certificate — it is a digital reference. There are two main types: defined CoS (for workers applying from outside the UK) and undefined CoS (for workers already in the UK switching or extending).

Who this applies to: Licensed UK sponsors assigning CoS to workers, and employers planning to sponsor someone for a Skilled Worker or other sponsored route visa.

Regulated by the Immigration Advice Authority

Two types of CoS

Defined vs undefined CoS.

Defined CoS

Used when the worker is applying for their visa from outside the UK. Each defined CoS must be requested individually from the Home Office before it can be assigned.

Out-of-country

Undefined CoS

Used when the worker is already in the UK — switching visa category, extending, or changing employer. Assigned from the sponsor's annual allocation without per-CoS Home Office approval.

In-country

CoS reference number

A 10-character alphanumeric reference. The worker enters it in their visa application to link to your sponsorship.

Digital ID

Validity period

A CoS is valid for 3 months from the date of assignment. The worker must submit their visa application within that window.

3 months

What's on a CoS

Information included in a Certificate of Sponsorship.

A CoS contains the agreed terms of the sponsored role. The worker uses this exact information in their visa application — and any inconsistency between the CoS and the visa application can cause refusal.

→Job title and SOC (Standard Occupational Classification) code

→Salary or hourly rate, and how it is paid

→Hours worked per week

→Job start date and end date (or sponsorship period)

→Main work location

→Confirmation that the role meets skill level and salary threshold requirements

→Sponsor's licence number and key personnel details

How CoS allocation works

Getting CoS to assign.

Defined and undefined CoS are managed differently within the SMS — and understanding the distinction matters before you commit to a hire.

→Undefined CoS: each sponsor has an annual allocation set when the licence is approved (or renewed). These can be assigned as needed up to the cap.

→Defined CoS: each defined CoS must be requested from the Home Office through SMS for each individual sponsored worker. Requests are typically approved within a few working days.

→If you need more undefined CoS than your annual allocation, you can apply for additional CoS during the year — supported by justification.

→Unused undefined CoS do not roll over indefinitely — allocations are reviewed each year.

The CoS process

From decision to assignment.

Assigning a CoS correctly is one of the most error-prone parts of sponsorship. Mistakes can cause visa refusal, compliance issues, or wasted fees.

→Confirm the role meets Skilled Worker requirements: SOC code, skill level, and applicable salary threshold

→For defined CoS, submit the request through SMS and wait for Home Office approval

→Prepare the CoS with accurate details — salary, hours, location, dates

→Assign the CoS through SMS — at this point the CoS fee is paid (£525 Worker route) along with the Immigration Skills Charge

→Provide the worker with the CoS reference number so they can apply for their visa

→Update SMS records with any changes during the sponsorship period

Common mistakes

Where CoS errors happen most.

→Salary on the CoS below the applicable Skilled Worker going rate for the SOC code

→Wrong SOC code selected for the role — leading to threshold or eligibility mismatch

→CoS assigned with start date before licence approval is finalised

→Discrepancy between CoS details and the worker's visa application (e.g. salary or hours)

→Using undefined CoS where a defined CoS was required (worker applying from outside the UK)

→Failing to withdraw a CoS that won't be used — reducing future allocation

Common questions

Questions employers ask us.

The Worker-route CoS fee — used for Skilled Worker, Health and Care, Senior or Specialist Worker, Scale-up and similar routes — is £525 per assignment. Temporary Worker route CoS (Charity, Creative, Seasonal, etc.) costs £55. The fee was £239 prior to the April 2025 fees uplift, so older blog content quoting £239 is out of date. The Immigration Skills Charge is paid separately at the same assignment moment.

Yes. A CoS can be withdrawn before the worker submits their visa application. After application, the situation becomes more complex — the worker's visa is linked to the CoS, and withdrawal can have consequences for both parties.

You can apply to the Home Office for additional CoS during the year, supported by business justification. Approval is not automatic — the request should be backed by clear hiring plans and operational need.

Yes — this is one of the main uses of undefined CoS. A worker on a Graduate, Student, or other in-country visa can switch to Skilled Worker by being assigned an undefined CoS, subject to meeting the route requirements.

Yes. A CoS is valid for 3 months from the date of assignment. The worker must submit their visa application within this window or the CoS expires and must be reissued (if still appropriate).

Related services & resources

Need help assigning a Certificate of Sponsorship?

Whether it is a one-off assignment or ongoing CoS management, Harveys Legal supports licensed sponsors through every stage of the process.

Book Consultation →View CoS / SMS Support

Harveys Legal supports immigration applications, sponsor compliance preparation and related legal processes. Final decisions remain with the Home Office or the relevant decision-maker.