When shipping internationally, except from within the European Union, any shipment is subject to customs clearance.
During customs clearance, the relevant authority of the country you are shipping to will inspect the contents of your shipment to ensure that these comply with local rules and regulations.
It is also during customs clearance when the local authority may impose duties and taxes on your belongings, or request additional documents from you if you are qualified for duty and/or tax exemption.
At times, a shipment may pass through customs without the need for inspection or additional documents. These instances are extremely rare, and duties and taxes may still apply.