As of 23:00/11PM (UK Time) on December 31, 2020, free movement will no longer apply and EU, EEA and Swiss citizens will require authorization to enter the United Kingdom.
Consequently, EU/EEA and Swiss nationals travelling to the UK for work or for more than 6-months study, will need appropriate entry clearance. Those who were residents in the UK before the end of free movement are entitled to apply for status under the EU Settlement Scheme (EUSS).
Entry clearance may appear as a vignette in a national passport, or it may be granted digitally. EUSS leave will be granted digitally.
For all other visits up to 6 months duration, no visa or entry clearance is required.
Furthermore, EU/EEA and Swiss national identity cards will remain valid for all passengers travelling to the UK until October 1, 2021. In regards to Irish Passport Cards and Identity Cards held by British Citizens from Gibraltar these will continue to be accepted indefinitely.
For more information, see also the following pages of the British Government: