Income Heads

It depends on what sort of activity the person is carrying.

Say, for instance if the person is a commission agent in business dealing, and he undertakes the venture quite often, such income would be under "profits and gains from business or profession".  On the otherhand, say if he is a salaried employee, and he ends up getting commission for any transaction not related to his profession and which is not quite often, it would come under "income from other source".  So it varies from case to case and one needs to apply his mind.

So, Identify his activity first,see if it can be appropriately classified in the first four heads, if not go for "IFOS".