https://www.epo.org/en/service-support/faq/searching-patents/asian-patent-information/korea/filing-grant/what-language

What language must I use for patent applications in Korea?

Since 1 January 2015, it has been possible to file applications in either Korean or English (before: only in Korean). If you file in English, you must submit a Korean translation within 14 months from the earliest priority date.

For PCT applications entering the national phase in Korea, you must submit a Korean translation within 31 months from the earliest priority date. For PCT applications with an international filing day on or after 1 January 2015, it has been possible to request a one-month extension of the time limit for submitting the Korean translation.

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