Set off of loss upto 50% of income?

Does anyone know about a provision that limits either inter or intra head set off of loss against income only upto the the extent of 50% of such income?

It might be from topic of assessment of various entities. I remember reading a question specifically on this in the Study Material for CA Final Old Course, but unable to recall exactly which topic or chapter in the book.

Any help would be appreciated. Thanks in advance!