Face coverings became mandatory in additional indoor settings in England and Scotland following a recent spike in coronavirus cases.
Places for the new settings in England include cinemas and funeral homes, and in Scotland banks and wonder salons.
Coverings also will become compulsory altogether public enclosed spaces in Northern Ireland from Monday.
It comes as new quarantine rules for travelers to the United kingdom took effect at 04:00 BST.
Anyone now arriving in England, Scotland, or Northern Ireland from Belgium, Andorra, and therefore the Bahamas will need to quarantine for 2 weeks. Equivalent rules have already been put in situ in Wales.
And lockdown measures were reintroduced in Preston from midnight after an increase in Covid-19 cases. Residents within the Lancashire city face stricter restrictions, which include banning separate households from meeting one another reception.