Britons are being urged to take out comprehensive travel insurance and check their mobile roaming policies if they are travelling to the EU after the end of the Brexit transition period.
Cabinet minister Michael Gove was also telling businesses to make last-chance preparations to minimise the disruption when the new relationship begins on Thursday.
Mr Gove warned the time to make the final preparations before the UK begins trading with its biggest trading partner under the new treaty “is very short”.
“In just three days’ time the Brexit transition period will end and we will have finally regained our independence,” Mr Gove added.
The trade deal brokered on Christmas Eve does not carry over the ban on roaming charges, but does say both sides must encourage providers to have “transparent and reasonable rates”.
Government guidance tells British travellers to check with their mobile provider to see what charges they will face.
Passports should also be checked so that on the day of travel they have at least six months left before expiry.
Ministers are also urging businesses to ensure they understand the new rules on importing and exporting goods between Great Britain and the EU, as well as the different rules when trading with Northern Ireland.
They must also consider how to make customs declarations on EU trade and hauliers should get a Kent Access Permit before entering the county.