Writing a test on this BS in about a week....
The tax act says any amount "received", "accrued" or "in favour of".
Clearly it did not accrue to you and it is not in your favour...that leaves received...which you did. So according to the act, you'd have to include it.
However, case law set a precedent that you don't have to include it. In the case Geldenhuys v CIR (1947 C) it was that "received by" means "Received by the taxpayer on his own behalf for his own benefit".
So you would ignore the amount received completely and not include it anywhere on your tax return.
If you earn interest on the money held then that will be taxable. It would have been better if the agreement had been in writing....but its too late now. If you put it into writing now then that will cause more problems than an oral agreement because the agreement has to have existed when the money was received.
Its not that easy unfortunately. E.g. In some cases you get taxed on a deposit...even if its paid back. Or if you are collecting money for a charity.