Prepaid or postpaid SIM in Korea — what do I need?

koinfo ops

Prepaid SIM: sold at the airport and convenience stores with only your passport — good right after arrival. Postpaid plan (monthly contract) and most budget carriers (알뜰폰): you need your Alien Registration Card and a payment method in your name. Many services (banking, deliveries, verification) need a number registered to you, so switch to your own postpaid or MVNO line once you have the ARC.