Certificate of Sponsorship (CoS): Employer's Guide

What is a Certificate of Sponsorship?

The CoS is generated and assigned by the employer, not by the Home Office. The Home Office checks the CoS details against the visa application during processing. This means the accuracy of the information is entirely the employer's responsibility from the point of assignment. The Home Office cannot correct or amend a CoS; only the employer can withdraw and reissue one, at the cost of another assignment fee.

The CoS record contains: the worker's name and date of birth, their passport number, the job title, SOC code, salary, weekly working hours, proposed start date, duration of employment, and the work location. Each of these fields is assessed during the visa application. An error in any of them can cause complications ranging from a Home Office request for clarification to a visa refusal. See our genuine vacancy guidance for how role descriptions are assessed.

Defined vs undefined CoS, which type do you need?

	Defined CoS	Undefined CoS
Used for	Workers applying for a new visa from overseas; workers switching status in the UK	Extensions and some in-country applications where the worker already has a Skilled Worker visa
Allocation required?	Yes, employer must request allocation from the Home Office before assigning	No, available automatically within the SMS licence allocation
How requested	Via an SMS allocation request; allow additional processing days	Not required; assigned directly from the SMS
Most common use	New hires from abroad; in-country switches from other visa routes	Visa extensions for workers already sponsored by you

For most employers hiring overseas workers for the first time, the defined CoS is the relevant type. When requesting allocations, request more than you expect to use in the immediate term, a surplus allocation does not create material ongoing cost, and having to make a further request mid-process delays recruitment timelines at a point when start dates may already be confirmed. See our application guide for full licensing context.

How to assign a CoS on the Sponsor Management System

CoS assignment is carried out through the Sponsor Management System on GOV.UK. Only your Level 1 or Level 2 SMS users can assign a CoS. Before starting the assignment, ensure all the required information is to hand, you cannot save a partial assignment and return to it.

1. Confirm your defined CoS allocation. Check the SMS to confirm you have sufficient defined CoS allocations available. If not, submit a request to the Home Office. Allow additional working days for allocation requests to be processed. They are not instant.
2. Gather all required information. You need: the worker's full name and date of birth exactly as on their passport; their passport number; the job title and SOC code; the annual salary; weekly working hours; the proposed employment start date; and the work location address.
3. Check the SOC code and going rate. Confirm the SOC code against the Home Office's current eligible occupations list. Confirm the salary meets both the general threshold (£41,700) and the occupation-specific going rate for that code. If there is a discrepancy, resolve it before assigning, not after.
4. Complete the CoS record in the SMS. Enter all details accurately. Write the job description field to describe the actual duties of the role, not a generic template. Check the start date: it should reflect when the worker will actually start, not the earliest date you would prefer.
5. Review before confirming. Read through the complete CoS record before clicking confirm. A CoS cannot be amended after assignment. If you identify an error after assigning, you must withdraw and reassign, at the cost of another fee. Prevention is significantly cheaper.
6. Provide the reference number to the worker. Once assigned, the worker needs the CoS reference number to complete their visa application. Note the expiry date: the CoS is valid for three months from assignment. Build this date into your recruitment timeline.

The job description field

The job description field in the CoS record is reviewed during both the visa application and any subsequent compliance check. A generic, copied description, particularly one that reads as if pulled from a template or another role, is a red flag for both the caseworker assessing the visa and the compliance officer assessing the employer. Describe the specific duties of this specific role in this specific business in plain, practical language.

CoS fees and who pays them

CoS type	Fee	Payable by	Transferable to worker?
Skilled Worker defined CoS	£525	Employer, at point of SMS assignment	No, unlawful to pass on
Skilled Worker undefined CoS (extension)	£525	Employer, at point of SMS assignment	No, unlawful to pass on
Temporary Worker CoS	£25	Employer, at point of SMS assignment	No, unlawful to pass on

The CoS fee must be paid by the employer. It cannot be deducted from the worker's salary, invoiced to them, required to be repaid, or included in any clause in the employment contract that would have the effect of the worker bearing this cost. The same prohibition applies to the Immigration Skills Charge. Breaching either of these rules is a sponsor duty violation and may also constitute an unlawful deduction from wages under employment law. See our costs guide for full financial planning context.

Common errors when assigning a Certificate of Sponsorship

Errors in CoS assignments are more common than many employers expect, particularly on the first few assignments before the process is embedded. The most frequently occurring are:

• Incorrect SOC code. The most consequential error. An incorrect SOC code either applies the wrong going rate threshold or misrepresents the nature of the employment. Both create problems: the worker may not meet the salary requirement for the correct code, and the Home Office may identify the discrepancy during the visa assessment or a compliance review.
• Salary below the going rate. Employers who check the general threshold (£41,700) but miss a higher occupation-specific going rate for the assigned SOC code create a visa refusal for the worker. Always check both thresholds before confirming the salary field.
• Inaccurate start date. If the actual start date is materially different from the CoS start date and the worker has already applied using the CoS, complications arise. Where the start date moves significantly before the worker has applied, withdrawing and reassigning with the correct date is the cleaner approach.
• Generic job description. A job description that reads as a template, or that does not describe the specific duties of this specific role, is a flag in visa assessments and compliance reviews. Write it as you would for an internal briefing document.
• Wrong working location. For roles that span multiple sites or that have changed since the CoS was assigned, the listed work location may not match where the worker actually works. Officers reviewing CoS records at compliance visits check whether the location listed corresponds to where the worker is actually based.

CoS expiry, what happens and how to manage it

A defined CoS expires three months from the date of assignment. If the worker does not submit their visa application within those three months, the CoS cannot be used and a new one must be assigned. The original fee is not refunded.

The three-month window is sufficient for most standard applications. It becomes a risk when:

• The worker faces delays in obtaining biometric appointment slots, particularly where demand is high
• The application requires additional documents, such as overseas qualifications assessments, that take time to obtain
• The start date has been pushed back after the CoS was assigned, reducing the effective window

Track CoS expiry dates actively. Add each expiry date to your compliance calendar. If it becomes clear that the worker will not be able to apply before the CoS expires, withdraw it proactively and reassign with the correct start date once the timeline is confirmed. Allowing a CoS to expire without use is not itself a compliance breach, but managing it actively is better practice than discovering the expiry after the fact.

CoS errors and their compliance implications

Individual CoS errors cause problems primarily for the worker, a visa refusal, a delay to the start date, or a request for clarification during processing. But patterns of CoS errors, or specific types of inaccuracy, carry compliance implications for the employer.

A compliance officer reviewing a CoS assignment where the job description does not match what the worker actually does, or where the salary was understated, or where the SOC code does not reflect the genuine nature of the role, may raise these as compliance concerns about the sponsor, not just administrative errors. The distinction between an honest mistake and a deliberate misrepresentation is not always how compliance officers approach what they find; the standard is whether the CoS accurately described the role at the point of assignment.

The practical implication: treat CoS assignments as compliance documents from the outset, not as administrative forms to be completed quickly. A few minutes of additional care at the assignment stage prevents a significant amount of potential difficulty downstream. See our compliance audit guidance for how your CoS assignments are assessed during Home Office visits.

Frequently asked questions

What is a Certificate of Sponsorship?

A Certificate of Sponsorship is a unique reference number generated by a licensed sponsor in the Sponsor Management System. It is not a physical document. The worker uses the reference number when applying for their visa. Each CoS is specific to one worker and one role, and contains the job and salary details the Home Office uses to assess the visa application.

What is the difference between a defined and undefined CoS?

A defined CoS is used for workers applying for a new visa from outside the UK or switching immigration status in the UK. It requires a pre-approved allocation from the Home Office. An undefined CoS is used primarily for visa extensions by workers who already hold a Skilled Worker visa with you as their sponsor. For most new hiring, a defined CoS is what you need.

How much does a Certificate of Sponsorship cost?

The CoS fee is £525 for Skilled Worker roles and £25 for Temporary Worker roles. The fee is paid by the employer at the point of SMS assignment. It cannot be passed on to the worker, deducted from wages, or included in a repayment clause.

What happens if there is an error on a CoS?

If identified before the worker applies, you can usually withdraw and reassign, at the cost of another fee. If the worker has already submitted their visa application using the erroneous CoS, the situation is more complex. The error may cause a visa refusal, a request for clarification, or, for significant inaccuracies, compliance scrutiny of the sponsor. Take legal advice before taking action on an error in a CoS that has already been used in a visa application.

How long is a Certificate of Sponsorship valid?

A defined CoS expires three months from the date of assignment. The worker must submit their visa application before it expires. After three months, the CoS cannot be used and a new one must be assigned (and the fee paid again). Track expiry dates and build them into your recruitment timelines.

Can a Certificate of Sponsorship be used for more than one worker?

No. Each CoS is specific to one worker and one role. If you want to sponsor multiple workers, each requires their own CoS assignment and their own assignment fee. A single CoS cannot be assigned to multiple people or reused.