When international customers buy a product in your store, their country can charge them duties on the shipment. Duties usually can be paid by customers on delivery. If your customers might have to pay any duties, then indicate this information in one of your store's policies or pages. Otherwise, customers might refuse to pay the unexpected costs and your shipments might be returned.
Taxes and customs duties depend on multiple factors:
Check with your local legal advisor to get to know more about applicable duties and taxes.