If you are a UK employer with a sponsor licence and you want to hire a worker from outside the UK on a Skilled Worker visa, you need to assign them a Certificate of Sponsorship. The CoS is the foundation of the entire visa application — a digital record that links your company, the specific job, and the specific worker in the Home Office system. Errors in the CoS are one of the single most common reasons Skilled Worker visa applications are refused. This guide covers everything UK employers need to know.
What Is a Certificate of Sponsorship?
A Certificate of Sponsorship is not a physical document. It is a unique reference number that exists in the Home Office's Sponsorship Management System (SMS). It contains all the key information about the sponsored employment: the job title, the SOC code, the salary, the working hours, the start date, the work location, and the worker's personal details.
The worker uses the CoS reference number when they apply for their Skilled Worker visa. The Home Office cross-references the CoS details against the visa application and the published salary thresholds. If everything aligns, the visa is granted. If there are discrepancies — even minor ones — the application may be queried or refused.
Defined vs Undefined Certificate of Sponsorship
There are two types of CoS, and the distinction matters for your hiring timeline.
Defined CoS — For Workers Outside the UK
Used when the worker is applying for their visa from overseas (entry clearance). Each defined CoS must be individually requested from the Home Office through the SMS and approved before you can assign it. Processing typically takes a few working days but can take longer during busy periods.
A defined CoS must be used within 3 months of being assigned. If the worker does not apply for their visa within this period, the CoS expires and you need to request a new one.
Undefined CoS — For Workers Already in the UK
Used when the worker is already in the UK and is switching visa categories (e.g., Student to Skilled Worker) or extending their stay. These come from a pre-allocated pool and can be assigned immediately without requesting Home Office approval. This makes the process significantly faster for in-country switches.
How to Assign a Certificate of Sponsorship
Step-by-Step Process
1. Log into the Sponsorship Management System (SMS)
Your authorising officer or level 1 user accesses the system using their credentials. Only authorised personnel can create and assign CoS.
2. Select the correct SOC code
This is the most critical step. The Standard Occupational Classification code determines the minimum salary (going rate) for the position and whether the role is eligible for sponsorship. Getting the SOC code wrong is one of the most common reasons for visa refusal. Read the detailed descriptions for each potential code and select the one that most accurately describes the actual duties of the role.
3. Enter the job details
Job title, salary (annual), working hours, start date, and work location. The salary must meet both the general threshold and the going rate for the SOC code — whichever is higher.
4. Enter the worker's personal details
Full name exactly as it appears on their passport, date of birth, nationality, and passport number. Every detail must match the visa application precisely. Typos cause refusals.
5. Pay the Immigration Skills Charge
Must be paid before or at the time of assigning the CoS. £1,000/year for large sponsors, £364/year for small/charitable. For a 3-year visa at a large company, that is £3,000 per worker.
6. Review and assign
Check every detail before finalising. Once assigned, the worker receives the reference number and can submit their visa application.
Salary Requirements: The Going Rate System
The salary on the CoS must meet two thresholds simultaneously:
1. The general salary threshold: £38,700/year (or £15.88/hour) for most roles
2. The going rate for the specific SOC code, published in the Immigration Rules
You must pay whichever is higher. For many roles — particularly in healthcare, construction, and specialist trades — the going rate exceeds the general threshold significantly.
Salary reductions that may apply:
• Immigration Salary List (ISL) roles: 20% discount on the going rate (general threshold still applies)
• New entrants (under 26, switching from Student visa, certain postdoctoral roles): 70% of going rate, minimum £30,960
• Health and Care Worker visa: Separate, lower thresholds apply
The Full Cost of Sponsoring a Worker
Key exemption: Workers on the Health and Care Worker visa route are exempt from the Immigration Skills Charge and pay a reduced visa fee and no Immigration Health Surcharge. For healthcare employers, this reduces the total cost per worker by £6,000 or more.
Common Mistakes That Cause Visa Refusals
The 6 Most Frequent CoS Errors
1. Wrong SOC code
The single most impactful error. The SOC code determines the going rate and whether the role is eligible. An incorrect code can mean the salary appears to meet the threshold when it actually does not, or that the role falls outside eligible categories entirely. Take time to verify the correct code against the detailed ONS descriptions.
2. Salary below the going rate
The salary must meet both the general threshold (£38,700) AND the going rate for the SOC code. Many employers meet the general threshold but fall short of the occupation-specific going rate. Always check the going rate for your specific SOC code before assigning the CoS.
3. Inconsistent details between CoS and visa application
The worker's name, passport number, and date of birth must match exactly between the CoS and their visa application. Even a middle name included on one but not the other, or a transposed digit in the passport number, can trigger refusal.
4. Not paying the Immigration Skills Charge
The ISC must be paid at the time of CoS assignment. If you haven't budgeted for it — particularly at volume — the process stalls before it starts.
5. Using the wrong CoS type
A defined CoS for someone already in the UK, or an undefined CoS for someone applying from overseas, will cause the visa application to fail.
6. Failing to report changes after assignment
If the role, salary, or location changes between CoS assignment and the visa decision, you must update the CoS. Failure to do so is a compliance breach and grounds for refusal.
Your Ongoing Sponsor Duties
Assigning a CoS is not a one-time action. It triggers ongoing compliance obligations that the Home Office monitors and enforces through scheduled and unannounced compliance visits.
You must:
• Keep copies of all sponsored workers' right to work documents, available for inspection
• Report if a worker is absent for more than 10 consecutive working days without permission
• Report if a worker does not start employment or leaves your company
• Report significant changes to role, salary, or work location
• Report changes to your company (address, ownership, mergers)
• Maintain accurate HR records that the Home Office can audit
• Make reports through the SMS within 10 working days of the event
Consequences of non-compliance:
• Sponsor licence downgraded from A-rating to B-rating (restricts new sponsorships)
• Sponsor licence suspended (cannot sponsor new workers during investigation)
• Sponsor licence revoked (all sponsored workers' visas are curtailed — they must find a new sponsor within 60 days or leave the UK)
Important: Revocation does not just affect the one worker where the issue arose. It affects every sponsored worker in your company. A compliance failure involving one employee can result in all your international staff losing their right to work in the UK. This is why maintaining robust, ongoing compliance processes is essential.
Do You Need a Sponsor Licence First?
Yes. Before you can assign a CoS, your company must hold a valid sponsor licence. This is a separate application that establishes your company as an approved employer for sponsoring overseas workers.
The sponsor licence application involves demonstrating that your company is a genuine business operating in the UK, that you have appropriate HR systems in place, and that you have designated key personnel — an authorising officer, key contact, and level 1 user — to manage the sponsorship system.
Processing times vary but typically take 8 to 12 weeks for standard applications. A priority service is available for approximately 10 working days at an additional fee. The sponsor licence costs £574 for small sponsors or £1,579 for large sponsors and lasts for 4 years before needing renewal.
How Recruitroo Supports UK Employers
For UK employers with a sponsor licence, Recruitroo manages the recruitment, CoS preparation, and visa application process as a single workflow. We source and screen candidates from our database of 30,000+ pre-screened international workers. When a candidate is selected, our system prepares all CoS documentation with pre-verified SOC codes and salary checks against current going rates.
We flag issues before the CoS is assigned — wrong SOC code, salary below the going rate, incomplete worker details — so that refusals are prevented rather than dealt with after the fact. We track the visa application from CoS assignment through to decision, and coordinate the worker's relocation.
For employers who do not yet have a sponsor licence, we provide guidance on the application process and can advise on the HR systems and processes needed to meet Home Office requirements.
Hiring international workers for the UK?
Tell us your roles. We'll check eligibility, calculate the full cost, and give you a plan within 24 hours.
This guide reflects UK immigration rules as of March 2026. Sponsor licence regulations, CoS requirements, salary thresholds, and going rates change frequently. Always verify the current position on gov.uk and in the Immigration Rules before assigning a Certificate of Sponsorship.