Firstly, you should check to see if you need to register your trailer or Caravan before you take it abroad, but if you’re driving in the EU, Andorra, Bosnia and Herzegovina, Iceland, Liechtenstein, Norway, Serbia or Switzerland, you don’t need a green card for either your vehicle or what you’re towing.
However, other countries may have different requests, including additional insurance, so it’s always best to check with your insurer to determine what’s needed.