Initially, the lockdown was for a three-week period, but this has been extended for at least another three more weeks, Foreign Secretary Dominic Raab announced on April 16.
Here's what you can and can't do under the guidance:
People are only allowed to leave the house for limited purposes
Residents are only allowed to leave their homes to shop for basic necessities - and as infrequently as possible.
One form of exercise a day allowed - for example a run, walk or cycle - alone or with members of your household.
You can leave the house for any medical need, or to provide care or to help a vulnerable person.
Travelling to and from work is permitted, but only when absolutely necessary and your job cannot be done from home.
All shops selling non-essential goods remain shut
All shops selling non-essential goods, including clothing and electronic stores, have closed.
Libraries, playgrounds, outdoor gyms and places of worship also shut as of Monday 23 March and will remain so until a decision to relax the current restrictions is made by the government.
Hotels, hostels, bed and breakfasts, campsites, caravan parks, and boarding houses for commercial or leisure use will also remain closed until further notice.
What shops remain open?
Supermarkets and other food shops, healthshops, pharmacies including nondispensing pharmacies, petrol stations, bicycle shops, home and hardware shops will all keep their doors open.
Other stores which can remain open include laundrettes and dry cleaners, bicycle shops, garages, car rentals, pet shops, cornershops, newsagents, post offices, and banks.
Cafes and restaurants which do takeaway or delivery, along with market stalls which offer essential retail, such as grocery and food are also allowed to continue trading.
All gatherings and social events are banned
Gatherings with more than two people, excluding people you live with, are not allowed under the lockdown rules. This includes weddings, baptisms, birthday parties and other ceremonies.
These measures do exclude funerals, but even here there are restrictions. Only immediate family will be able to attend and people must observe social distancing rules.
What happens if I don't follow the rules?
Anyone who is not following the rules faces a fine or even a criminal record. Police have powers to disperse gatherings or inappropriate behaviour - such as having a barbecue on the beach - and they have used these powers.
Most parks are open for exercise, but some have temporarily shut after people flouted the rules.
How long will the lockdown be extended?
The restrictions are being kept under constant review but the government is not committing to a date.
During the Downing Street press briefing on April 16, when Dominic Raab announced a further three week extension, he insisted “there is light at the end of the tunnel” but refused to set out a “definitive timeframe” for easing the lockdown measures.
Coronavirus: Everything you need to know