Outward Processing Relief (OPR) allows EU traders to temporarily export goods from the EU for processing/repair in a non-EU country and then claim full or partial duty relief when the goods are re-imported. This enables traders to gain advantage from cheaper labour costs, or processes that aren't available within EU countries. Note that you cannot claim any refund or remission of import duties or any refunds or other benefits under the Common Agricultural Policy.
Before claiming any duty relief under the OPR procedure you must apply for an OPR authorisation and ensure your exported goods and the process or repair they are to undergo are eligible for duty relief using the OPR procedure. The goods you're exporting must either originate in the EU or Turkey, or have been imported to free circulation within the EU or Turkey with all customs formalities completed and customs charges paid in full.
This guide explains how OPR works and the advantages your business can gain by applying for authorisation to use the system.