Almost any shipment crossing international borders is subject to duties and taxes imposed by the importing country.
When shipping UPS or FedEx internationally you need to indicate on the shipment who pays the duty and tax:
Take care to choose your options carefully. If a if the customer gets hit with a big fees they could reject the package.
Please Note: Certain marketplaces, like Amazon, require the merchant to assume this tax. Please check with the originating marketplaces's policies.