How to Get a SIM Card in South Korea: Passport to Postpaid, Step by Step

The rule that decides everything

Korea requires real-name registration for every mobile line, and the documents a person can use depend on their status. This single rule drives every other decision.

• Prepaid lines can be opened with a passport alone. You do not need an alien registration card (ARC).
• Postpaid plans require a Korean registration record — for foreign residents that means an ARC, plus usually a Korean bank account for automatic billing.
• MVNOs (resellers such as altteulpon, 알뜰폰) follow the same identity rules as the major carriers for postpaid plans.

So before you buy anything, ask one question: do you have your ARC yet? If no, you are buying prepaid. If yes, postpaid and MVNO plans open up. This is not a carrier preference — it is the identity-verification framework that every provider follows. No provider will open a postpaid account on a passport alone.

Before your ARC: prepaid, and where to buy it

Without an ARC, the practical option is a prepaid SIM or eSIM opened on your passport. This covers your first days or weeks while the ARC application is in process. If the pre-registration window is your specific situation, our guide to getting a phone plan without an ARC goes deeper on the verification gap and how to pick a prepaid you can port later.

Where you buy matters for price:

• Airport counters (Incheon and Gimpo, plus Busan and Jeju) are the most convenient — staff are used to arrivals and it is the fastest way to get connected. Tourist prepaid is priced for convenience, so it is usually the most expensive per gigabyte.
• Convenience stores and online pickup are cheaper. Many arrivals pre-order a SIM online and collect it at the airport or a city pickup point.
• Some sellers offer eSIMs that activate with a QR code, which works if your phone supports it and you prefer not to queue.

The key limitation to understand up front: prepaid numbers frequently fail Korean identity verification. Banking apps, delivery services and government portals verify the caller against the resident database, and a passport-based prepaid line often cannot pass that check. Treat prepaid as a bridge, not a destination.

After your ARC: postpaid and MVNO

Once your alien registration card is issued, the higher-value options open up:

• Postpaid plans from SK Telecom, KT and LG U+ — the three major carriers — require your ARC and usually a Korean bank account for billing. You sign a monthly plan with a data allowance.
• MVNO plans resell the same three networks at lower prices. Coverage and speed match the host network; the savings come from support and bundling. Signing up generally requires the same ARC and bank account as postpaid.

The important move: port your existing number. Number portability works between carriers and MVNOs, including from prepaid to postpaid. If you have already given your prepaid number to a landlord or employer, porting it beats starting over with a new number. Ask for portability explicitly when you switch.

For a detailed comparison, see our guide to MVNO plans in Korea and whether an MVNO is worth it.

The common mistakes to avoid

Most problems with getting a SIM in Korea come from ordering the steps wrongly:

• Buying prepaid and expecting it to behave like a full plan. If you rely on Korean apps, prepaid verification will fail on some of them. Budget for that gap until you register.
• Buying the phone before checking band compatibility. Imported handsets should be unlocked and support Korean network bands. Confirm before buying a plan.
• Throwing away the prepaid number. If you port it to postpaid, everything tied to the old number (apps, bank OTPs) survives. Cancel without porting and you start the verification cycle again.
• Assuming an eSIM is automatically a full line. A data-only eSIM gets you online but gives you no Korean phone number for verification. If you need a number, buy a SIM that includes one.

A clean order of operations: passport → prepaid on arrival → apply for ARC → port to postpaid or MVNO → then do identity-dependent things like banking. Get that sequence right and the SIM question stops being a problem.