Wearing a face covering in shops and supermarkets in England is to become mandatory from 24 July.
Those who fail to comply with the new rules will face a fine of up to £100, the government is to announce.
The move will bring England into line with Scotland and other major European nations like Spain, Italy and Germany.
Since mid-May, the public have been advised to wear coverings in enclosed public spaces, where they may encounter people they would not usually meet.
It has been compulsory on public transport since 15 June.
Health Secretary Matt Hancock is expected to set out the new guidance on face coverings on Tuesday.
They are designed to minimise the spread of coronavirus and also encourage people to return to the shops safely.
The announcement follows confusion about the government's intentions in recent days, with a senior minister suggesting on Sunday that people should use their "common sense" rather than being compelled to cover up.
Labour said ministers' response had been "slow and muddled" and questioned why the new rules would not come into force for 11 days.