What is the difference between 「利益」 and 「利潤」? They both mean "profit". When shoud I use each of them?
As per my knowledge, 利潤 is used as Profit in economical terms. Where as, 利益 can be used as gains/returns in terms of advantage. For example:
利潤：もちろん、利潤は生産費を上回るべきです。 Benefits of course should exceed the costs. 利益：利益になるような本を読みなさい。 Read the kind of books that teach you something.
As you can see, 利益 is usually used in terms of benefit or advantages. But 利潤 is almost always used for monetary profits. I am saying almost, because I am not a native myself.