The UKCA timeline is outlined here

23rd June 2016

The UK votes to leave the European Union

31st January 2020

The UK leaves the European Union

1st February 2020

11 month transition period begins

31st December 2020

End of the transition period

1st January 2021

UKCA mark required for products on UK market

1st January 2022

CE mark no longer accepted in UK

1st January 2023

All UKCA mark to be permanent marking*

*Non-permanent marking is permitted before this date. This can be an adhesive label on the product or packaging. Permanent marking required after this date