For courier service, if the duty tax is less than the amount specified by the customs, the courier company will make a prepaid to the customs and later on collect it from the consignee during delivery (on the spot), if the consignee refuse to pay, this duty tax will be charge to shipper together with an admin fee. If the duty tax is greater than the amount specified by the customs, the shipment will be on hold in customs and the courier company will try to contact the consignee to confirm payment. If the consignee refuse to pay, the shipment will be return and the shipper will not liable for duty tax.
For Mail/Parcel service, the shipment will be on hold in post office and required the consignee to go to post office to pay for the duty tax in order to retrieve it. Shipper are not liable for duty tax.