You usually have to pay them before your goods are released from customs in the destination country. Carrier(UPS,DHL, FEDEX) may be able to pay on your behalf(if you have their account or you have signed agreement with them)to ensure your goods are released quickly – and they’ll invoice you for the charges (Generally with small hanlding fee)
When sending goods internationally it's important to have a complete understanding of a shipment's total costs (also known as landed costs). Other charges that apply to your shipment along the way can include:
To find out more, ask your carrier for advice, or browse the customs website of the country you're shipping to.