Table Of Content
- Background
- What is a Certificate of Sponsorship?
- Which Visa needs a Certificate of Sponsorship?
- A correct Certificate must be assigned.
- Defined COS and Undefined COS
- Defined COS
- How to apply?
- Who can apply?
- Undefined COS
- How to apply?
- Who can apply?
- Another key difference between Defined COS and Undefined COS
- Conclusion

Background
Before December 2020 overseas nationals looking to work in a skilled role needed to apply for a UK Tier 2 (General) visa. These applicants needed to obtain a certificate of sponsorship from the UK-based employers they were applying to work for. On the other hand, employers in order to hire foreign workers needed to apply for sponsor licenses. After obtaining a sponsor license they could assign a certificate of sponsorship to the applicants. They could assign either restricted COS or unrestricted CSO.
The UK Tier 2 (General) Visa was replaced by the UK Skilled Worker from January 2021. So, from this time foreign workers looking to work in the UK need to apply for a UK Skilled Worker Visa instead as a Tier 2 (General) Visa no longer exists. Applicants still need a certificate of sponsorship assigned by a licensed employer under the UK Skilled Worker visa category. UK employers also still need a sponsor license after which they can assign certificates of sponsorships.
Until December 2020 there were 2 types of certificates of sponsorships. They were called ‘restricted certificate of sponsorship’ and ‘unrestricted certificate of sponsorship’. After the introduction of the UK Skilled Worker Visa, the restricted and unrestricted COS were revised and renamed as ‘Defined Certificate’ and ‘Undefined Certificate’. Restricted and unrestricted COS is no longer issued.
What Is A Certificate Of Sponsorship?
Certificate of Sponsorship is not a physical document but an electronic record. This electronic record confirms the details of the migrant worker you wish to employ, the job they will do, their qualification, their salary, etc. You must assign COS to the foreign applicants from outside the UK or inside the UK (while applying to switch to a UK Skilled Worker Visa) you want to hire to work in your organization. Each COS has a unique number which applicants are required to enter when filling out their worker visa forms.
There are 2 types of COS:
- Defined COS and
- Undefined COS
Restricted certificates are now termed as defined COS, and unrestricted certificates as undefined certificates.
Which Visa Needs A Certificate Of Sponsorship?
Before you can assign COS, you need a sponsor license. The license you need depends on whether the workers you want to fill your jobs are:
- ‘Workers’ – for skilled or long-term employment. For Example – Skilled Worker Visa, Senior or Specialist Worker Visa, Minister of Religion, and International Sportsperson.
- ‘Temporary workers’ – for specific types of temporary employment. For example – Scale-up Workers, Creative Workers, and Charity Workers, Religious Workers, and Graduate trainees.
So, if you want to hire foreign workers on visa routes mentioned here you need to assign a certificate of sponsorship to them. You can also apply for a license that covers one or both types of workers.
A Correct Certificate Must Be Assigned.
The employers must assign the right type of COS to the applicants under the Skilled Worker route Visa which is a point-based system. A Point-based system means applicants need to earn a total of at least 70 points ( points are awarded for various factors such as salary, qualification, etc.) for a Skilled Worker Visa.
You as an employer must understand the difference between defined and undefined COS so that you assign the correct COS to the applicants. If you assign the wrong certificate to the applicant your sponsor license may be revoked.
Defined COS And Undefined COS
There are 2 types of COS you can assign on the Skilled Worker Route. They are termed as Defined COS and Undefined COS. There are some key differences between the two.
Defined COS
If you are going to sponsor a foreign worker who is applying for entry clearance from outside the UK you must apply for Defined COS for them. You must provide details of specific jobs and salaries while applying for defined COS. You cannot assign COS until your application for defined COS has been approved. However, you can apply for a defined COS if you have not decided on which foreign individual you want to hire but think that you need to hire a foreign worker in the foreseeable future. You must have a genuine vacancy and salary details of the position the migrant will fulfill.
How To Apply?
You need to apply for a defined COS on the Home Office’s SMS (Sponsorship Management System) each time you need one to assign to a foreign worker. You don’t get an annual allocation for it. However, you can apply for more than one defined COS in a single application. You can only assign COS when you have one in your SMS account. It usually takes one day to process the application for a defined COS unless more information is required.
Who Can Apply?
Only A-rated sponsor license holders can apply for defined COS.
You need to choose a category from a drop-down list when you assign an undefined COS. You can choose the category based on the worker’s current immigration status and whether you will need to pay the immigration skill charge for them.
Undefined COS
When you are going to sponsor someone who is applying from within the UK to switch to a UK worker visa or you want to bring an intra-company transfer visa assignee you need to assign them undefined COS. Unlike defined COS you can request for a certain number of COS for the first year while applying for an undefined COS.
How To Apply?
Similar to the undefined COS you can apply for undefined CSO on your company’s SMS system. There is no cap on the number of undefined COS you can apply for but because you have to pay the fees for assigning each undefined COS you need to know how many you require. After applying you get a certain number of annual COS allocations in your SMS account. You can utilize the allocated number of COS in 12 months’ time. But if there is a situation where you need to assign more than the allocated number of COS in your account you can apply to increase your allocation.
Who Can Apply?
A-rated sponsor can apply for undefined COS. B-rated sponsors can apply for undefined COS if the existing worker is applying for permission to stay from within the UK and they sponsored the applicant which led to their last grant of permission.
Another Key Difference Between Defined Cos And Undefined Cos
You should know the clear difference between the two so that you don’t make a mistake while applying for COS and assigning it to the applicants. You must not assign:
- A Defined COS to a worker for any other job that is different from the one you described in your COS application
- An Undefined COS to a worker applying for entry clearance
Conclusion
A Certificate of Sponsorship is a mandatory requirement while recruiting foreign talents. Sponsoring companies must provide the details of workers, the job offered, the salary offered, the educational qualification of the worker, and other details to make a successful COS application.
Defined and Undefined COS has different properties and you need to apply accordingly based on your requirements and the requirements of the type of COS you are looking to apply.
Read Other Blogs:
How to Maintain Your UK Sponsorship License
What is a UK Sponsorship License and why is It Essential for Employers