Difference between EUR1 and ECCO

An EC Certificate of Origin is a non-preferential document that certifies what the origin of the products is in a shipment. This may be requested by a client or for import compliance.
For example, textiles shipped from the UK to Argentina require an EC Certificate of Origin.
An EUR1 is used for countries where the EU has preferential trade agreements, an EUR1 is required so that it confirms the goods shipped of EU origin and the products can have preferential import duty applied to them.