Calculate landed cost (duties, taxes, fees) for cross-border checkout

Steps

1. Identify a landed-cost provider (examples include Avalara Cross-Border, Zonos, or carrier-native tools such as FedEx International Shipping Assist) and integrate their API at the checkout rate-shop step.
2. Send the provider the destination country, shipper country of origin, HS code for each line item, declared value per unit, quantity, and shipping cost — these are the inputs required to compute duty and tax.
3. Receive the breakdown: import duty (ad valorem rate applied to customs value), destination VAT or GST (applied to customs value plus duty), and any merchandise processing fee or other government charges.
4. Present the landed cost total at checkout and collect it from the buyer — this is Delivery Duty Paid (DDP) Incoterm; if you present only item price and ship DDU/DAP, the buyer faces unexpected carrier brokerage bills on delivery.
5. Store the duty and tax breakdown against the order so you can remit collected VAT/GST to the destination tax authority or reconcile against actual customs entry totals.
6. Refresh rates before finalizing each order, not just on page load, because duty rates and VAT rates change with regulatory updates.