Drivers from Northern Ireland travelling to the Republic of Ireland will need an insurance green card from January due to Brexit.
The issue first came to the fore during Brexit negotiations and it has now been confirmed the measure will apply when the transition period ends.
The Irish Department of Transport told the BBC that a green card would be required for drivers from Northern Ireland.
"A green card is a document issued by your insurer that proves you have motor insurance cover when driving in another jurisdiction," a Department of Transport spokesperson said.
"As it stands, following the transition period, a green card will be required for vehicles from the UK, including Northern Ireland, being driven in Ireland or other EU Member States, unless the European Commission declares otherwise."
The spokesperson also confirmed it was not an offence for vehicles from Northern Ireland or Great Britain to travel in the Republic of Ireland without a GB sticker.
The green card may not be required if the matter is resolved in the UK and EU's post-Brexit deal.
Talks resumed this week in London amid fears that time was running out for a deal to be reached before the transition period ends on December 31.
The Department for the Economy had previously estimated that there are approximately 110 million border crossings between Northern Ireland and the Republic each year.
A green card is an internationally recognised insurance document which provides proof of the minimum compulsory motor insurance cover required by the country visited.
The cards provide a guarantee of insurance for a minimum of 15 days and can remain valid until the expiry date of the motor insurance policy, providing cover for multiple trips.
Currently all motor vehicles with a valid registration travelling within the EU are covered by the terms of the EU Motor Insurance Directive (MID).