Anyone travelling into Northern Ireland who plans to stay for at least 24 hours will have to self-isolate on arrival, according to new restrictions.
The measures are contained in a newly published paper from the executive.
However, the paper says that people who routinely cross the border for essential purposes will not be subject to restrictions.
It also details a week-long “stay-at-home curfew” coming into force in NI on Boxing Day.
Analysis by Enda McClafferty, BBC News NI political editor
Ministers advise and the public decide – that is the challenge for the executive with this latest piece of guidance
It sets out what the public should do during the stay-at-home curfew and when travelling from GB and the Republic but not what they must do
Health Minister Robin Swan would like to strengthen the stay-at-home message with some legal authority. He set out his case in a letter to the first and deputy first ministers over the weekend.
The massive drop in compliance from the public is a big concern for the executive with the prospect of more house parties over the festive period now laced with the added danger that the new variant of the virus is likely to be in circulation here.
Ministers are banking on personal responsibility because they know if their advice is not heeded the health service will pay the price in the new year.
The new travel guidance lists what qualifies as essential travel during that period of time including for work and health reasons.
The guidance states that people should only travel within Northern Ireland when it is absolutely necessary.
It says that essential travel includes:
On Sunday, the executive agreed so-called Christmas bubbles should be limited to one day.
The move followed action in England, Scotland and Wales on Saturday, cutting the previously agreed five days to just one.
Earlier, the executive decided a new six-week lockdown must be introduced from 00.01 GMT on 26 December, which will be reviewed after four weeks.
Northern Ireland’s politicians are not in agreement on how to best handle to current level of risk.
Sinn Féin called for an all-Ireland-Great Britain travel ban and, in a late-night vote on Monday, the SDLP supported this.
However, Alliance, the DUP and UUP voted against.
Some 40 countries, including the Republic, have banned UK arrivals due to concerns about the new variant.
In the Republic of Ireland, anyone travelling from Britain must self-isolate for 14 days.
That means staying in their room – regardless of negative test results – from the date of their arrival.
There will be an increased Garda presence on Irish roads but road blocks will not be placed on the border to prevent travel between Northern Ireland and the Republic.
Northern Ireland’s new restrictions will come on the same day that the Department of Health advised people who are classed as clinically extremely vulnerable to no longer attend work if they cannot work from home.
It added that “people are free to make their own judgements… depending on the Covid-security of their working environment”.
Chief medical officer Dr Michael McBride said: “This strengthened advice is intended to offer enhanced protection from Covid-19 to the most vulnerable people in our society.
“It is not a return to shielding as we knew it at the outset of the pandemic.”
“We are not advising CEV people to stay permanently indoors, and I would encourage CEV people to continue to go outside for exercise, provided they observe social distancing when they do so”.
The health minister has highlighted the updated guidance for visiting people in care homes over Christmas.
Covid-19 testing is available to one visitor per care home resident per week over the Christmas period and up to Friday 8 January 2021.
More details are available on the Department of Health website.
A further 16 coronavirus-related deaths were recorded in Northern Ireland on Tuesday, bringing the total number of deaths recorded by the Department of Health to 1,219.
There were also a further 439 cases of Covid-19 diagnosed. There are 447 people with Covid-19 in hospital. Thirty are in intensive care, with 23 on ventilators.
Meanwhile, the Northern Ireland Statistics and Research Agency (Nisra) has released analysis of pre-existing medical conditions among Covid-related deaths in Northern Ireland.
In cases between March and November, there were 1,406 deaths where Covid-19 was mentioned on the death certificate.
The vast majority of these people had pre-existing health conditions.
Just 8% of Covid-19-related deaths (114) in that period involved no pre-existing condition.
Nisra also provided more detailed analysis for deaths between March and September.
The most common pre-existing conditions among Covid deaths in that six-month period was dementia and Alzheimer’s disease.