As I wrote in my blog “Import Documents You May Need When Exporting” I explained various customs documents, one of which was the EUR.1
The EUR.1 Certificate is a Certificate of Origin of sorts. It is used for exporting goods to, or importing goods from the European Union to countries with which the EU has Free Trade Agreements. Depending on the agreement for certain goods you have to pay lower import duties, or even no import duties at all. This is called the preferential rate.