To claim a VAT (Value Added Tax) refund when leaving Paris via Eurostar at Gare du Nord, you must visit the Customs (Détaxe) area before you board. After passing through the French passport control but before the UK border checks, look for the PABLO kiosks. You must scan the barcoded tax-free forms provided by the retailers where you made your purchases. If the screen turns green, your refund is electronically validated. If it turns red, you must present your forms, the unused goods, and your passport to a Customs officer at a nearby desk for a manual stamp. Once validated, you can drop your forms into the designated tax-free mailboxes located in the departure lounge if you chose a credit card refund, or visit a nearby currency exchange desk if you requested cash. It is recommended to arrive at the station at least 90-120 minutes early, as queues at the kiosks can be long during peak times.