1973 Public Bond Issuance Act Article 4

The term for redemption of each issue of the Bond is six years. The payment of the principal shall begin three years from the issue date. The principal shall be paid once per year, and fully paid up in four installments of one-fourth of the principal each.
中文原文 中華民國六十二年度公債發行條例第4條
本公債各期債票償還期限,定為六年。
於發行之日起,屆滿三年,開始還本;每年還本一次,每次還本四分之一,分四次還清。

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