A government information campaign is being launched to help UK travellers planning to visit the EU after the Brexit transition period ends in December.
Anyone booking a European trip for 2021 will be urged to check a dedicated web page at gov.uk/transition to check the specific actions they may need to take.
The UK will no longer be following EU rules from January and travellers may need to take extra measures.
These may include having health insurance or an international drivers licence.
It also warns people that they may be unable to travel unless their passports are valid for at least another six months from their date of travel.
And passports must be less than 10 years old.
The campaign will include advertising in online and print publications, as well as on social media.
The advice says people may need to buy health insurance as European Health Insurance Cards will no longer be valid.
Some countries may not recognise UK driving licences so travellers who want to drive will need to apply for an international driving permit.
The new process for getting permission to take pets into the EU will take four months to complete.
UK mobile phone users will no longer benefit from automatic free data roaming.
Wendy Morton, the minister for the European neighbourhood, said the campaign would help travellers “by bringing together all the information they need to know in one place so they can plan in advance and get on with their trip”.
UK residents made 67 million visits to EU countries in 2019, according to ONS figures.
Abta chief executive Mark Tanzer said: “Europe is home to some of the most popular destinations for British holidaymakers.
“Many people will be making plans for travelling to Europe next year, so Abta and its members are keen to work with the UK government to make customers aware of any changes that will affect their travel arrangements.”
Which? Travel editor Rory Boland warned: “These potential changes to European travel will affect millions of holidaymakers, who may have already booked holidays for 2021 and will now have to factor in additional costs associated with travel insurance and data roaming, and for some the price of renewing their passport earlier than expected.
“From 2021, EHIC cards may no longer be valid, so consumers should ensure their travel insurance policy includes adequate medical cover.
“Some mobile phone providers have said they have no plans to change roaming charges following Brexit, however holidaymakers should check with their provider before travelling.”