Interesting, it seems like this might be a UK vs US thing. All the non-dodgy UK results for "income" I found agree with what I thought e.g. "Income less Costs = Profit" [1]
The one exception is HMRC (UK equivalent of IRS) which, for the purposes of corporation tax only, defines income like profit [2] (with some technical differences, but the same spirit). But for other purposes (e.g. personal income tax) even they use it to just literally mean cash received without subtracting off outgoings.
Using it in this net sense seems very odd to me, but maybe that's because I'm British. "Income" and "outgoings" look to me like symmetrical terms, and no one would consider outgoings to be after subtracting off money coming in (would they?!)
That page says that "net income" message the sense you meant it and "gross income" means the sense I understood it.
It does say that unqualified "income" means the net version but it's a push to say that makes it unambiguous. (And, at I said on a sibling comment, this seems to be a US convention.)
This is incorrect as anyone who has looked at a financial statement or taken a first level accounting class will know - Revenue is the top line, the gross income and lastly net income, the two reflecting the removal of various costs/expenses as per GAAP.
Income (in a business) is another word for revenue. I think you meant: business tax is assessed on profit.