Q: If a person works for a consultancy firm, like McKinsey, in the Corporate Finance Practice, would his income be halal? I’ve mentioned a few websites below to give you an idea about McKinsey’s operations in general as well as particularly about Corporate Finance Practice, and, also, I’ve placed a link to let you know what a management consulting firm generally does.
A: We have browsed through the websites you suggested and according to the explanations given on these sites, the work a consultancy firm does is generally permissible. I say generally because these firms deal with a wide range of corporate companies. So if they need to provided management consultancy to a brewery company for example, or a casino or gambling concern, it will not be permissible for a Muslim to offer his services in that field and he shall have to ask his company to excuse him and replace him with a non-Muslim colleague.
Other than that the income derived from working for this company is totally halaal
And Allah Ta’ala knows best
Mufti Siraj Desai