A Certificate of Sponsorship (CoS) is a unique reference number — not a paper certificate — issued by a UK employer that holds a sponsor licence. You cannot apply for a Skilled Worker visa without one.
Who issues a CoS
Only employers who hold an active Worker licence on the Home Office Register of Licensed Sponsors. Every employer listed on our site is cross-checked against this register so you don't waste time applying to an employer that cannot sponsor you.
Defined vs undefined CoS
Defined CoS are for overseas applicants — the sponsor must request one from the Home Office for each candidate. Undefined CoS are for in-country switchers and are drawn from the sponsor's annual allocation.
Common reasons an employer says no
- They don't hold a sponsor licence — this is the most common reason. Use our verified-sponsor filter to avoid these.
- The role doesn't meet the salary or skill threshold.
- They've used their annual undefined CoS allocation (rare).
- They have a policy of not sponsoring — even though they could.