Guide · as of 2026-08-09
Phone and SIM in Korea: Prepaid, Postpaid, 본인인증
A Korean SIM splits into two regimes: prepaid (선불), which can be activated on a passport alone and works from day one, and postpaid (후불), which requires an ARC and usually a Korean bank account or credit card for billing. The dividing line that matters is not price but identity verification (본인인증): a number registered to a passport frequently fails the SMS verification used by Korean banks, government sites, delivery apps, and ticketing. This is the single most reported friction point for new arrivals.
All Korean SIMs are name-registered; anonymous SIMs do not exist under the telecom real-name rules (전기통신사업법 및 전기통신사업법상 부정가입 방지 제도). Registration is against either a passport (prepaid, short-term) or an ARC (postpaid and prepaid alike once the card exists).
Prepaid (선불)
- Sold at airport counters (KT, SK, LG U+ roaming desks), convenience stores in partnership with MVNOs, and online MVNO storefronts.
- Passport-only activation for stays under 90 days; an ARC can be registered later or from the start.
- Typical structure: fixed-day passes (30/60/90-day unlimited-data SIMs aimed at tourists) or rechargeable balance plans (unverified: current per-operator pricing).
- Number portability from prepaid to postpaid is possible but requires the ARC and, at some operators, in-person conversion (unverified: per-operator conversion rules).
Postpaid (후불)
- Requires ARC; billing via Korean bank account auto-debit or Korean credit card. Some carriers accept a security deposit in lieu of credit history (unverified: current deposit amounts).
- Two channels: the three MNOs (SKT, KT, LG U+) with retail stores and contract discounts, and several dozen MVNOs (알뜰폰) reselling the same networks SIM-only, without contracts, at monthly prices commonly in the ₩10,000–40,000 range depending on data allowance (unverified: representative current plan prices).
- MVNO sign-up is predominantly online and itself requires 본인인증 or a Korean credit card plus ARC scan, another circular dependency; MVNO brands with physical desks (airport, Homeplus/emart partnerships) and MNO stores resolve it in person.
The 본인인증 problem
Korean web services verify identity through carrier-based SMS authentication (휴대폰 본인인증) operated against the subscriber registry, or through the PASS app. Verification succeeds when the name, birth date, foreigner flag, and phone subscriber record all match, in effect requiring:
- a number registered under the user’s own name (not a friend’s, not a corporate line), and
- registration keyed to the ARC identity, since services compare against the alien registration record.
Passport-registered prepaid SIMs fail this comparison at most services even though calls and data work normally. Re-registering the same number under the ARC at the carrier after alien registration fixes verification without changing the number. PASS app enrollment for foreigners requires the ARC-registered line plus, in some flows, an additional ARC authenticity check against the immigration database (unverified: current PASS foreign-user flow). Banking apps increasingly accept alternatives, such as certificate-based login (공동인증서/금융인증서) and in-app ARC scanning, but account opening and most first-time sign-ups still route through carrier verification.
Sequence implied by the dependencies: prepaid SIM on arrival for connectivity; ARC application; after the ARC arrives, either re-register the prepaid line or port to postpaid; then 본인인증-dependent services (banking apps, 정부24, HomeTax, Coupang payment verification) become available.