Britons could face being fined £200 if they turn up at an airport without a new form proving they have an essential reason to travel from Monday.
The Department for Transport (DfT) said from Monday, people travelling internationally from England will need to complete and carry a declaration to travel document.
The three-page form, announced by the government in January, includes information on why someone is leaving the country.
Currently, international travel from England is only allowed for limited reasons, such as work, volunteering, education, medical grounds and funerals.
According to Boris Johnson's roadmap for easing coronavirus lockdown restrictions, people in England will not be allowed to go on foreign holidays until May 17 at the earliest.
The DfT said police have been stepping up patrols at ports and airports in recent weeks and will have the power to ask travellers to produce a completed form, which can be printed or stored on a mobile phone, from Monday.
Anyone found to be trying to travel internationally without a valid reason will be sent home and could receive a fixed-penalty notice for breaking stay at home rules.
The fines start at £200 and double for each incident, up to a maximum of £6,400.
The introduction of the fines comes as a new survey suggested that three out of four people (75%) would be willing to carry proof they have been vaccinated if it meant they could travel.
The poll of 2,014, commissioned by London City Airport, found that acceptance of some kind of proof to travel was highest among people aged over 65 (89%), falling to 67% for 18-24-year-olds.
Prime Minister Boris Johnson has pledged that all UK adults will be offered their first dose by the end of July.