ROI

There is no set rule – in practice it is most commonly calculated at the end of the year using the closing balance.

It depends on the wording of exam questions. Sometimes you are only given the closing capital employed in which case there is no choice.

Although using the average balance is logical when you are given both opening and closing balances, the examiner often uses the opening balance (if given) on the basis that it is the assets at the start of the year that earned the profit.

I do not believe that our notes say anywhere that we should take the opening balances (although do correct me if I am wrong 🙂 ), and I do assume that you are not using the notes without watching the lectures because that would be completely pointless.