Enforcement Rules of the Government Procurement Act Article 19

For limited tendering procedures where there are only two tenders received from the two or more suppliers invited to compete, the procedures may be proceeded. Where there is only one tender received, the procedures may be altered to proceed as if only one supplier were invited.
中文原文 政府採購法施行細則第19條
機關辦理限制性招標,邀請二家以上廠商比價,有二家廠商投標者,即得比價;僅有一家廠商投標者,得當場改為議價辦理。

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