Boysey,
it's not a super profits tax - it is charged virtually at the EBIT line - meaning paid on ALL PROFITS, super or not.
Companies work out profits after expenses and tax (at normal 30% rate) then get slugged an extra 40% on that. Works out 58% marginal tax rate.
Make $1 profit after tax, pay 40c to gov't.
Also no franking credit available to company - so goodbye to fully franked dividends.