Shipments outside of the USA (for orders produced in the USA) or shipments outside the EU (for orders produced in Europe) may trigger customs fees.
This depends on the destination country, the order value, the country limits, and product-depending factors.
Your end customer is responsible for these particular fees. Those need to be paid to the appropriate customs agency or delivery provider.
Customs agencies mostly calculate duties/fees based on the declared retail price that the customer paid to you.
Please note that we are currently not providing options to submit a VATID/GST ID or similar data on the shipping labels.