Travelers to England from abroad will from 4am GMT on January 15 be required to show proof that they have had a negative COVID-19 test up to three days before their departure, the government said in a statement.
The new rule was announced earlier in January as authorities try to ramp up protection against new, more infectious strains of the coronavirus from other countries.
Travel into and out of Britain is at very low levels currently due to lockdowns which ban visits abroad for most people.
Providing details of its new policy, the government said that transport operators would need to check that passengers had proof of a negative test before they boarded their flight, train or ferry, and there would also be checks on arrival.
Fines starting from 500 pounds ($677.40) will be issued to passengers and transport operators who do not comply with the new rules.
There will be a very restricted number of exemptions, including hauliers, to allow the free flow of freight, and air, international rail and maritime crew.
The test must be of a diagnostic-standard test such as a PCR test, and could in some cases include LAMP and lateral flow tests within set limits, the statement added.
The pre-departure test requirement is in addition to quarantine rules which require arrivals from abroad to self-isolate for ten days, unless they opt to have a COVID-19 test after five days and it is negative, releasing them early.