Green card
Green card for Bulgaria
Bulgaria accepts the Greek plate as proof of insurance.
Not needed. The card helps in an accident with a foreign driver, though. Ask your insurer for it. Own damage cover and roadside assistance apply there only if the territorial limits of the policy say so.
Check the whole trip, with each country on the road · The green card, the full guide
Other countries with the same answer
Serbia, Romania, Montenegro, Bosnia and Herzegovina
Sources: Motor Insurers Bureau of Greece, the UK bureau, the Polish bureau.