Cut off marks for both prelims and mains are decided by UPSC after the result of civil services exam but before declaring the final result the cut off marks are released and it is the marks of last candidate who gets selected based on the number of vacancies for respective categories.

the reason behind the difference between cut off marks in various coachings is that they prepare their own answer keys and they release the cut off on the basis of comparison between previous year's results.

ALWAYS GO FOR THE OFFICIAL CUT OFF THROUGH THE OFFICIAL WEBSITE OF UPSC.

goodluck

dear aspirant,

The UPSC does not use the term ‘cut-off’. It prefers the term ‘minimum qualifying mark’.  This mark is simply the mark of the last candidate in the merit list prepared by the UPSC. The list is in the descending order of the marks obtained. The merit list is prepared according to the number of vacancies in every category for a particular year. For example, if there are 300 vacancies for OBC category in a year, the mark of the last candidate in the OBC list (of 300) would be the cut-off for that category.Hence it depends upon the vacancies that might be the reason for the variation.

2018 upsc cut off was 98.00 for general , 96.66 for OBC,84.4 for sc and 83.34 for st.

hope it helped.