Import & Custom taxes are usually based on the item's price, shipping weight, dimensions and country of origin. Orders delivered to a particular country will have to adhere to that country’s local import & custom duty. The parcel’s recipient, your buyer, may need to pay these to clear the parcel through customs..
Which is why you must always inform your buyers about the potential import charges (tax and custom charges) that they will need to pay when they receive their items so there are no unpleasant surprises on their end.
You should state it in your listing’s item description as well as communicate it to your buyers again when they have made their purchase. Doing this is not only the Best Practice for a responsible seller but would also help you reduce the number of buyer’s remorse returns protected by the eBay Money back guarantee policy.