Do you know the difference
between a Defined and
Undefined CoS?

Are some sponsors confused by the two types of Certificate of Sponsorship (CoS), and unsure of the differences between a defined and an undefined CoS? The Home Office seems to think so, since they have recently issued a reminder for employers on when to use each type of certificate.

Before a foreign national can apply for a visa to work in the UK, they must be issued with a valid CoS from their employer. A CoS is not a physical document, but instead takes the form of an electronic record containing a unique number which the worker must use to apply for their visa. Once a CoS has been assigned to a worker, they must use it to apply for their visa within three months.

If you are sponsoring Skilled Workers, you must ensure you understand the difference between defined and undefined Certificates of Sponsorship and assign the correct type to each worker. You must not assign:

  • A defined CoS for a job other than the one described in the application for that CoS
  • An undefined CoS where a defined one is required.

Sponsors who do either of the above are committing a compliance breach and therefore risk having their sponsor licence revoked by the Home Office. Below, we set out the differences between the two types of CoS and explain when and how to use each one.

Understanding the difference

The two types of CoS are:

  • Defined Certificate of Sponsorship – For Skilled Workers applying for entry clearance from outside the UK (excluding Intra-Company Transfer (ICT) route).
  • Undefined Certificate of Sponsorship – For Skilled Workers applying for permission from within the UK, or for workers on all other routes such as the ICT route.

If your business has been sponsoring workers on Tier 2 visas before the Skilled Worker route launched on 1 December 2020, you may be more familiar with the terms ‘restricted CoS’ and ‘unrestricted CoS’. When the Home Office produced updated Guidance for Sponsors to coincide with the Skilled Worker route opening, the terminology was changed and restricted CoS were rebranded as defined CoS, and unrestricted CoS became known as undefined CoS.

Defined CoS

If you want to recruit a migrant worker under the Skilled Worker route and they will be applying for leave to enter the UK from overseas, they will need to be assigned a defined CoS. You must be an A-rated sponsor to apply for a defined CoS.

Sponsors must submit requests for defined certificates to the Home Office on a case-by-case basis using the online Sponsorship Management System (SMS). Once approved, defined certificates will appear in your SMS account and you can then assign them to a worker. You do not need to have identified a candidate in order to apply for a defined CoS, but you will need to confirm specific job and salary details of the role the migrant worker will fill.

You cannot have an annual allocation of defined CoS, and you must apply for one using a separate process each time you need one. Detailed instructions on how to apply for a defined CoS using the SMS can be found here.

Undefined CoS

If your employee will be applying for a Skilled Worker visa from within the UK, or if you are bringing in an assignee on an Intra-Company Transfer visa, you will need to issue them with an undefined CoS.

Unlike defined certificates, sponsors do not need to submit individual requests for undefined CoS. This type of certificate can be issued to a worker immediately, as long as the sponsor has a certificate available in their annual CoS allocation.

When a business applies for a sponsor licence, they will be asked to estimate how many undefined certificates they think they will need for Workers and Temporary Workers in the first year. You must be able to justify your request and the Home Office may ask for further information before making a decision on your allocation.

Once the Home Office has decided your CoS allocation, the certificates (if any) will be allocated to your SMS account. You will then have up to 12 months to use them. This is known as your ‘CoS year’ (or ‘allocation year’).

Before your CoS year expires, you will need to request a renewed allocation of undefined certificates using the SMS, otherwise your allocation could reset to zero when the 12-month period comes to an end. If your business runs out of certificates during your allocation year, you can make a request for additional CoS allocation using the SMS.

Detailed guidance on requesting a renewal of annual allocation using the SMS can be found here.

Sponsorship advice and support

Smith Stone Walters has a dedicated sponsor licence team who are experienced in helping businesses of all sizes to manage the sponsorship process. Our immigration consultants can act as a Level 1 user on your SMS account, which allows us to monitor the status of your CoS allocation and when you need to renew, as well as other essential day to day administration relating to your licence.

To find out how we can help, please call 0208 461 6660 or email

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