Does the cost of duties & taxes (USA to Canada) change depending on the carrier: USPS or FedEx?

[fitnessvids7]

Hello, question...

I recently shipped an item to a residential address in Canada, while I'm based in the US. The customer selected FedEx International Ground and the actual cost of shipping was ~$28.00. However, the customer contacted us and sent pictures of an invoice FedEx included with their package for $102 CAD.  This has not happened before (to this extent), and I'm unsure how to proceed until I have a better understanding.

For starters, we do state in our policy that the customer only pays for the transportation cost, and duties & taxes are also their responsibility. But we do not include that in the checkout page. So, I'm thinking that we'll offer some type of compensation/refund as a courtesy. But that doesn't help me understand the why.

• The order totaled to ~$244 for 12 items. Would the cost of duties and taxes really be $102 CAD for this?
• Why does FedEx leave the package with an invoice, rather than hold the package until the invoice is paid?
• Would have shipping via the USPS resulted in less duties and charges?
• Any additional input is appreciated

Thank you