Chief medics have reduced the coronavirus self-isolation period from two weeks to just 10 days.
The UK's four chief medical officers said on Friday that they are confident "we can reduce the number of days that contacts self-isolate".
This means that those returning from abroad, as well as those who think they may have symptoms or are a close contact of someone with the virus, must stay at home for just 10 days.
The change will apply in Northern Ireland, England and Scotland from 00:01 on Monday 14 December.
It already applies in Wales.
In a joint statement, the CMOs said: "Self-isolation is essential to reducing the spread of COVID as it breaks the chains of transmission.
"After reviewing the evidence, we are now confident that we can reduce the number of days that contacts self-isolate from 14 days to 10 days. People who return from countries which are not on the travel corridor list should also self-isolate for 10 days instead of 14 days.
"People who test positive should continue to self-isolate for 10 days from onset of symptoms or 10 days from point of taking a positive test if asymptomatic. We urge everyone to self-isolate when appropriate, it will save lives."
Northern Ireland Covid-19 Apps - StopCOVID NI app and COVIDCare NI - will be updated to reflect the changes from Monday 14th December.
The letter was signed by:
Chief Medical Officer for Northern Ireland, Dr Michael McBride
Chief Medical Officer for England, Professor Chris Whitty
Chief Medical Officer for Scotland, Dr Gregor Smith
Chief Medical Officer for Wales, Dr Frank Atherton
