Certificate of Sponsorship (CoS): The 2026 Guide for UK Employers

A Certificate of Sponsorship (CoS) is an electronic record a licensed UK sponsor assigns to a migrant worker before that worker can apply for a sponsored visa, such as the Skilled Worker visa. It is not a paper certificate: it is a unique reference number generated through the Sponsor Management System (SMS), and choosing the wrong type – defined or undefined – is one of the most common causes of visa delay we see.

This guide is written for UK employers, HR teams and overseas businesses expanding to the UK. It covers the two CoS types, how allocations work, the fees involved, realistic timescales, and the mistakes that stall recruitment. Conroy Baker Ltd is a team of IAA-regulated Immigration Advisers supporting employers across the UK, the US, Canada, Europe and the Middle East.

• What it is: a unique electronic reference number, assigned via the SMS, valid for one visa application.
• Two types: defined (out-of-country Skilled Worker applicants) and undefined (in-country applicants and most other sponsored routes).
• Fee: £525 per CoS for Skilled Worker and Senior or Specialist Worker routes
• Use-by rule: the worker must apply for their visa within 3 months of the CoS being assigned
• Defined CoS decision time: usually within one working day; longer if UKVI requests further information

Figures stated as at 12 July 2026. The Home Office updates fees and rules regularly – always check the current position before assigning a CoS.

Every worker you sponsor needs one. If your business holds a sponsor licence – or is applying for one via our Sponsor Licence Application service – you cannot bring a sponsored worker to the UK, or switch them into a sponsored route, without first assigning a CoS.

The routes that require one include the Skilled Worker visa, the Senior or Specialist Worker route, the UK Expansion Worker route, and other Global Business Mobility categories. For overseas companies establishing a first UK presence, the CoS is the operational link between your Expansion Worker sponsor licence and the people you actually need on the ground.

Getting this wrong is the single most frequent CoS error we correct. The distinction is simple once stated plainly.

A defined CoS is for Skilled Worker applicants applying from outside the UK. You request each defined CoS individually through the SMS, stating the role, salary and occupation code. UKVI normally decides the request within one working day, though requests are sometimes held for further checks – a genuine business, a genuine vacancy and a credible salary are what UKVI is testing.

An undefined CoS covers Skilled Worker applicants applying from inside the UK (for example, switching from the Graduate route) and workers on most other sponsored routes. Undefined certificates come from an annual allocation you request when you apply for your licence, then renew each licence year. If your allocation runs out mid-year, you must request an increase – and this is where recruitment plans most often stall.

1. Confirm the role is eligible. Check the occupation code, the going rate and the general salary threshold for the route. An ineligible role invalidates everything downstream.
2. Check your allocation. For undefined certificates, confirm you have headroom in the current licence year. For defined certificates, prepare the individual request with accurate role and salary detail.
3. Assign through the SMS. A Level 1 User completes the assignment. Accuracy matters: the details on the CoS must match the employment contract and the visa application exactly.
4. Pay the CoS fee and, where it applies, the Immigration Skills Charge. The Skills Charge is a separate, often underestimated cost that scales with sponsorship length and company size. Use our free UK Sponsorship Cost Calculator to see the full cost of a sponsored hire before you commit.
5. The worker applies within 3 months. Once assigned, the clock runs. A CoS that expires unused is money and time lost.

The CoS fee itself is only one line of the true cost of sponsorship. Employers should budget for:

• CoS fee: £525 per certificate for Skilled Worker and Senior or Specialist Worker routes
• Immigration Skills Charge: £364 per year (small sponsors/charities) or £1,000 per year (medium and large sponsors), payable up front for the full sponsorship period
• The worker’s visa application fee and Immigration Health Surcharge – often reimbursed or shared by agreement, and relevant to your total hiring budget.

Two rules protect you here. First, certain costs – including the CoS fee and the Skills Charge – cannot lawfully be passed to the sponsored worker. Second, always date your internal budget: the Home Office typically revises fees at least once a year.

Most CoS problems are avoidable. These are the ones we resolve most often:

• Requesting the wrong type. A defined CoS assigned to an in-country applicant (or vice versa) usually means starting again – and losing weeks.
• Exhausted undefined allocations. Growing employers routinely hit their annual ceiling mid-recruitment. Allocation increase requests are not always quick, and there is no reliable priority route when capacity is limited.
• Mismatched details. A salary or job title on the CoS that differs from the contract invites refusal and compliance scrutiny.
• Assigning before eligibility is settled. If the occupation code or salary is wrong, the CoS fee is spent and the visa fails anyway.
• Ignoring the 3-month window. Delayed applicants mean expired certificates and repeated fees.

In one recent engagement, a UK employer’s undefined CoS allocation request remained delayed despite repeated follow-ups, with the priority route unavailable due to capacity limits. Recruitment plans and an employee’s immigration timeline were at risk. We reviewed the allocation request history, assessed the compliance position, and escalated the matter through the appropriate legal channels with UKVI. The escalation succeeded: the sponsorship process progressed and the business-continuity risk was contained. The lesson for employers is simple – allocation delays are not always a waiting game; there are structured escalation routes when the delay threatens the business.

Every CoS you assign is a compliance commitment. UKVI expects the role, salary and working pattern to remain as stated, and expects changes to be reported through the SMS within strict deadlines. Weak record-keeping around assigned certificates is a recurring theme in licence suspensions. If your SMS housekeeping has drifted, our SMS Compliance service exists precisely to put it right before UKVI finds it first.