Not enough information as we don't know where the buyer is. However I will try an educated guess.
Depending on their location buyers often have to pay VAT or GST on purchases, and import taxes if buying from outside their country. Etsy collects the VAT/GST in most locations, but customs departments in the buyer's country collect the duties where applicable and the buyer must pay these before they can receive the goods. There is nothing you can do about this, buyers need to be aware of their country's taxes and duties before buying from outside their country. You can't help them with this, refer them to Etsy.
