Dear Aarifa,

Every college declares its cut-off which is the minimum percentile required for the candidate to qualify for the next round of selection process. The cut-offs generally depend on the factors like number of candidates appearing for the test, difficulty level of the paper, number of seats available, reputation of the college and many such factors. IIM A, IIM B, IIM C & IIM L have already declared their cut-offs for CAT 18.

To know more about this in detail, I suggest you to visit:
https://bschool.careers360.com/articles/cat-cutoff

Good Luck.

There is no maximum minimum score..each college shall decide its own cutoff percentile. For all IIMs cutoff scores sharedbelow under CAT:

https://bschool.careers360.com/articles/cat-cutoff

Minimum score of 75 percentile is good enough for lower end colleges and for higher end colleges minimum 90 percentile is must.