What documents will be required to be able to stay in the UK for a study or work period from 2021?

If you arrived in the UK before 31 December 2020, you should have applied for the EU Settlement Scheme. Your pre-settled or settled status will be used as evidence of your rights in the UK. If you have not applied but believe you are eligible to apply, please see the guidance on late applications

If you first entered the UK after this date, you will have to apply for a visa under the new Immigration System.