It is correct that a Green Card is not required by law to cross borders within the European Union. This is because every EU country complies with the First Directive on Motor Insurance which says that every insurance policy issued in the EU must provide the minimum insurance cover required by law in any other EU country. 

Green Cards are also not necessary for some non-EU countries who are signatory to Section III of the Internal Regulations, which is an international agreement between Green Card Bureaux.  These countries are Croatia, Iceland, Norway, Switzerland (incorporating Liechtenstein) and Andorra.

A Green Card is required for travel to other signatory countries of the Green Card System (see list below).

Whlst under no legal obligation to do so, many insurers will issue a Green Card.  If they will not, you may wish to make enquiries with other insurers or enquire into the possiblity of obtaining border insurance at the point of entry into the country.

You should be aware that the Green Card document itself is only proof that the minimum third pary liability cover required by law in the visited country is in force.  You should check with your insurer to make sure that the full UK policy cover is in force when you travel abroad whether or not a Green Card is issued.

There is also a practical consideration beyond the strict legal position outlined above and that is, even within countries where frontier inspection is no longer required, the Green Card is still the insurance document most readily recognized and understood by national police forces. As you may need to produce evidence of insurance other than at a border (i.e. after an accident) you may consider it advisable to carry a Green Card to avoid inconvenience.

To find out if a Green Card is necessary or not please see the list of countries below:

GREEN CARD NOT NECESSARY

Andorra

Austria

Belgium

Bulgaria

Croatia

Cyprus

Czech Republic

Denmark

Estonia

Finland

France

Germany

Greece

Hungary

Iceland

Ireland

Italy

Latvia

Lithuania

Luxembourg

Malta

Netherlands

Norway

Poland

Portugal

Romania

Slovak Republic

Slovenia

Spain

Sweden

Switzerland

GREEN CARD NECESSARY

Albania

Bosnia and Herzegovina

Belarus

FYROM - Former Yugoslav Republic of Macedonia

Israel

Islamic Republic of Iran

Moldova

Morocco

Serbia and Montenegro

Tunisia

Turkey

Ukraine