New rules allowing travellers returning to England to take lateral flow tests instead of more expensive PCR tests will come into force later.
From 04: 00 BST, fully-vaccinated people arriving from a non-red list country can use a lateral flow test on, or before, day two of their return.
The government said the move was a “huge boost” for the travel industry.
Wales will make the same change a week later. Scotland and Northern Ireland have indicated they may follow suit.
Before then, anyone travelling on to the other UK nations in the 10 days after arrival in England must follow the rules for testing and quarantine in those places.
The latest change to the travel rules in England comes in time for many families going on half-term holidays.
The lateral flow tests for returning travellers must be bought from private providers – NHS kits cannot be used – with prices listed on the government website starting at £19.
Passengers need to book tests before travelling to the UK. They must send a picture of their lateral flow test to verify the result, and failure to do so could result in a fine of £1,000.
The change also applies to under-18s who live in the UK, whether or not they are vaccinated.
Travellers will still need to complete a passenger locator form before they return.
The Department of Health said that anyone who tested positive would have to take a PCR test, which they could get free through the NHS.
Health Secretary Sajid Javid said: “I’m delighted that from today eligible travellers to England, who have had the life-saving Covid-19 vaccine, can benefit from a cheaper lateral flow test, providing faster results.
“This huge boost to the travel industry and the public will make it easier and cheaper for people to book holidays and travel abroad.”
Dr Jenny Harries, chief executive of the UK Health Security Agency, said it was “critical” that people with positive lateral flow tests “get this checked” with an NHS PCR test.
“This way we can continue to monitor new variants and stay on top of the virus,” she added.
Since 4 October, fully-vaccinated passengers travelling to the UK from any non-red list country no longer have to take a Covid test before setting off.
People who are not fully vaccinated – and are 18 or over – still have to self-isolate at home for 10 days after arrival in the UK.
‘Job isn’t finished’
Meanwhile, Prime Minister Boris Johnson has repeated his call for people to get their booster jabs as the UK reported more than 40,000 daily Covid cases for the 11th day in a row.
On Saturday there were 44,985 cases recorded and a further 135 deaths within 28 days of a positive coronavirus test.
Mr Johnson, who has so far resisted calls by some health experts to reintroduce Covid restrictions despite rising infection levels, said: “Vaccines are our way through this winter.
“We’ve made phenomenal progress but our job isn’t finished yet, and we know that vaccine protection can drop after six months.
“This is a call to everyone, whether you’re eligible for a booster, haven’t got round to your second dose yet, or your child is eligible for a dose – vaccines are safe, they save lives, and they are our way out of this pandemic.”
People eligible for boosters include anyone aged 50 and over, those living and working in care homes for the elderly, and frontline health and social care workers.
Prof Stephen Powis, NHS England’s national medical director, warned the country faced the prospect of a “tough winter”.
Writing in the Sunday Telegraph, he said vaccines remained “the strongest weapon in the armoury” and urged people to get their booster jabs to “protect the freedom and Christmas that we have all earned”.
On Saturday, a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), which advises the government, said he was “fearful” there could be another lockdown Christmas if measures were not brought in soon.
Prof Peter Openshaw told BBC Breakfast: “We all really, really want a wonderful family Christmas where we can all get back together.
“If that’s what we want, we need to get these measures in place now in order to get transmission rates right down so that we can actually get together and see one another over Christmas.”