How do 주민센터 and 구청 work in Korea?

These are Korea's local government offices, and knowing which does what saves you trips. The 주민센터 (community service center, now often called 행정복지센터) is the smallest, most local unit at the neighborhood (dong) level, and it handles everyday administrative tasks: registering your address or a move (전입신고), issuing residence and other certificates, applying for local welfare and childcare programs, and often selling official garbage bags (종량제봉투). The 구청 (district office) covers a whole district (gu) and handles bigger matters such as business registration, building and property paperwork, larger civil affairs, and district-wide services.

As a rule of thumb, go to the 주민센터 first for personal, everyday paperwork, and the 구청 for business or larger official matters. A key point for foreigners: your visa and Alien Registration Card are handled by Immigration (출입국·외국인청), not by these offices, so do not go to the 구청 for ARC issues. After you have your ARC, though, you do report address changes at the 주민센터 like everyone else. To prepare, bring your ARC and passport plus any relevant documents (a lease for address registration, for example), and expect queues on weekday mornings and lunch hours. Larger offices in international areas have English-capable staff, and a translation app helps elsewhere. You can also do a growing number of these tasks online through the Government24 (정부24) portal once your identity verification is set up.