How do I get a certificate of employment (재직증명서 or 경력증명서) in Korea?

Quick distinction first. A 재직증명서 proves you currently work somewhere, while a 경력증명서 covers your past or total work history including dates and position. You usually need one for visa renewals at immigration, opening certain accounts or loans, renting an apartment, or applying to a new job.

The easiest way to get one is to ask your company's HR or general affairs team directly, and most companies issue it within a day. It typically includes your name, your registration or passport number, job title, department, employment start date (and end date on a 경력증명서), and the company's official stamp. If immigration or a bank needs the official version, make sure HR adds the 직인, the company seal, otherwise it may not be accepted. At larger companies you can often download it yourself from the internal HR portal. If you need an English copy for use abroad, ask HR whether they can issue a bilingual one, and if not you may need a certified translation. Keep both a PDF and a stamped paper copy, since some offices still want the original.