Regulations Governing the Handling of Mail Article 23
The term “prompt delivery mail” refers to a mail item that is delivered within a time limit with the payment of an extra charge.
中文原文 郵件處理規則第23條
國內郵件加付限時費，按班限時投遞者，為限時郵件。
English translation for reference only; the Chinese text prevails. Not legal advice.