Defined CoS vs Undefined CoS

In This Article

• What are the two types of CoS?
• Defined CoS — entry clearance from abroad
• Undefined CoS — in-country applications
• Side-by-side comparison
• The allocation process
• Which type do you need?
• Common mistakes to avoid
• Frequently asked questions
• Related terms

What are the Two Types of CoS?

The Home Office distinguishes between two categories of Certificate of Sponsorship based on whether the visa applicant is currently inside or outside the UK:

• Defined CoS — For workers applying from outside the UK (entry clearance applications)
• Undefined CoS — For workers already in the UK switching visa categories or extending an existing visa

This distinction matters because the two types are allocated and approved through completely different processes.

Defined CoS

A Defined CoS is required when a worker is applying for a UK visa from their home country or any country other than the UK. It is called "defined" because the employer must apply to the Home Office for each individual CoS before it can be assigned to the worker.

Key characteristics:

• Each Defined CoS must be separately requested and approved by the Home Office
• There is a monthly cap (pool) on the total number available nationally
• Applications are assessed — UKVI checks that the role and salary meet the rules before granting the CoS
• Once approved, the employer assigns it to the named worker
• The worker then uses the CoS reference number in their visa application from abroad

Processing time: Defined CoS applications can take several weeks, particularly for roles outside the Immigration Salary List. Employers should plan months ahead for international hires.

Undefined CoS

An Undefined CoS is used when the worker is already in the UK and is either:

• Switching from one visa category to another (e.g., student to Skilled Worker)
• Extending their existing Skilled Worker visa (often with a new employer)

It is called "undefined" because the employer does not need prior Home Office approval for each CoS. Instead, sponsors receive an annual allocation of Undefined CoS from the Home Office (based on their historical usage), and they draw from this pool as needed via the Sponsorship Management System.

Key characteristics:

• Drawn from the employer's pre-allocated annual supply — no per-CoS approval needed
• Faster to assign once the allocation is in place
• Used only for workers physically in the UK
• The worker then includes the CoS reference in their in-country visa application (permission to stay)

Side-by-Side Comparison

The Allocation Process

Undefined CoS allocation: New sponsors receive a small initial allocation of Undefined CoS. As they build a track record, allocations increase. Sponsors can request additional CoS via the SMS if they run out. Approval of additional allocation is not guaranteed and can take time.

Defined CoS allocation: There is no pre-allocated supply of Defined CoS. Each one must be applied for individually. The Home Office sets a monthly limit on the total number it will approve across all sponsors combined. Demand-heavy periods (e.g., start of a new tax year) can make approval slower.

Which Type Do You Need?

Note: Applicants who entered the UK on a Standard Visitor visa cannot switch in-country — they must return home and apply with a Defined CoS.

Common Mistakes to Avoid

• Assigning an Undefined CoS for a worker who is abroad. This is invalid and will lead to a visa refusal.
• Starting the Defined CoS application too late. Factor in Home Office processing times, especially during peak periods.
• Running out of Undefined CoS allocation without topping up. Request additional allocation proactively; don't wait until you've run out.
• Confusing entry clearance with permission to stay. The terminology on the SMS can be confusing — double-check which application type the worker will be making.

Frequently Asked Questions

Can a worker use an Undefined CoS if they are temporarily in the UK on a business visa?

No. Workers who entered the UK on a Standard Visitor visa cannot switch in-country. They must leave the UK and apply with a Defined CoS for entry clearance.

How many Undefined CoS does a new sponsor get?

New sponsors typically receive a small starting allocation (often 5–10). They can apply for more through the SMS, providing justification for the additional numbers needed.

Can the employer reassign a CoS to a different worker?

No. Once a CoS is assigned to a named worker, it cannot be reassigned. If the original worker does not proceed, the CoS must be withdrawn and a new one issued for the replacement candidate.

Is there a different fee for Defined vs Undefined CoS?

The CoS itself has no direct fee. The Immigration Skills Charge is the same regardless of which type of CoS is used. The difference in cost comes from the application process — Defined CoS requests may require more preparation time.

Related Terms

• Certificate of Sponsorship
• CoS Expiry & Validity
• Sponsor Licence
• Changing Visa Sponsors

Browse thousands of UK employers currently offering Skilled Worker visa sponsorship. Search jobs →