Negotiable Instruments Act Article 28

The drawer may make a statement in the bill to the effect that interest will be paid on the amount of the bill at a specified rate.If an interest rate is not specified, it shall be fixed at 6 percent per annum.Except as otherwise agreed upon between the parties, interest shall accrue from the drawing date.
中文原文 票據法第28條
發票人得記載對於票據金額支付利息及其利率。
利率未經載明時,定為年利六釐。
利息自發票日起算。
但有特約者,不在此限。

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