Evidence of payment — $50 or more

(1) If an expense of $50 or more was incurred under this Act by or on behalf of a registered party, a registered association, a nomination contestant, a candidate or a leadership contestant and paid by an agent or other person authorized under this Act to pay such an expense, the agent or other person shall keep a copy of the invoice prepared by the person who provided the good or service to which the expense relates setting out the nature of the expense together with proof that it was paid.