You have just clearly identified the problem: it's a discretionary decision.
We suggest that the proposed legislation include the possibility of revising an invoice, but without changing the date of the current proper invoice. That way, there will be no discretion. This will not allow Her Majesty to negotiate a new invoice in order to extend the payment period or defer the duty to pay.
This amendment has merit, although Mr. Sorbara thinks it is unnecessary. If we always rely on ministerial and government discretion, we can sometimes be very disappointed. It is better to include it in the proposed legislation to ensure that the discretion granted will not be misused.