You as the “importer” pay all customs duties. Parcels are subject to random checks by Customs. If customs duties incur, they will be due when the parcel arrives in the target country. Either the logistic partner pays the duties in advance (most often you may pay this to our partner DHL or FedEx after the delivery, they will charge you later via letter), or you will be asked to pick up that parcel in a post office where you have to pay the duties.
(Normally we ship via incoterm DAP, freight can be handled differently)