Importing Goods - HST/GST Tax as single expense?

pkeiller

As a business in Ontario I have to charge (and pay) the blended GST/HST rate of 13% on most transactions. Ordinarily this calculation goes off without a hitch.
That said, in some instance I need to be able to modify the actual amount of tax charged or paid. For example; duty on an imported shipment. The cost to clear the shipment with Canada Post or UPS might be minimal (say $10 to $25), however, the amount of tax paid could be much larger (it is based on the value of the shipment and not the services).

Is there a way I can modify the amount of tax showing on a bill to reflect what was actually paid and not what was calculated?

Thanks in advance.