Right to work in the UK
As an employer, you must check that any job applicants are allowed and have the Right to Work in the UK before you can employ them. You can be fined up to £20,000 if you cannot show evidence that you checked an employee’s right to work in the UK.
check the applicant’s right to work online here at the DWP
You don't need to check existing employees from the EU, EEA, or Switzerland if they came to the UK on or before before 1 July 2021.