The minimum qualifying mark in the preliminary stage for the UPSC exam varies each year based on factors like the total number of candidates and exam difficulty. Generally, candidates need to secure at least 33% marks in the General Studies Paper II (CSAT). However, passing this paper alone isn't sufficient; candidates must also score well enough in General Studies Paper I to rank high enough for selection to the mains. Qualifying marks can fluctuate, reflecting the competitive nature of the examination and the need for strategic preparation for both papers.