UK motor insurance policyholders will need to carry an International Certificate of Insurance or Green Card while driving in the European Economic Area (EEA) and other areas of Europe if the UK leaves the EU on the 29th March 2019 without “a deal” or where alternative arrangements have not been made by member states. A deal was reached in May 2018 to waive the requirement but to date this has not been ratified by the European Commision.
As its stands, if there is a “no deal” Brexit you must carry a green card with you to drive legally in Europe, failure to do so could involve prosecution, a fine and your vehicle being impounded.
You will require a green card to drive in the Republic of Ireland.
You will require separate green card for any trailer attached to your vehicle.
You will need to produce the Green Card upon request by authorities and in the case of an accident. You do not need to carry a European Accident Statement but this is highly advisable as indeed it is currently as it can help greatly in ensuring that the details of any incident are correctly recorded.