National Health Insurance Act Article 58

From the date of withdrawal, no benefits shall be payable for a beneficiary who withdraws from coverage according to Article 13; the Insurer shall return all extra insurance premiums. If the benefits have already been received, the beneficiary shall return them to the Insurer.
中文原文 全民健康保險法第58條
保險對象依第十三條規定應退保者,自應退保之日起,不予保險給付;保險人應退還其溢繳之保險費。
已受領保險給付者,應返還保險人所支付之醫療費用。

English translation for reference only; the Chinese text prevails. Not legal advice.