The information needed for duty free clearance varies country-by-country. In some instances, simply a packing list will suffice. In other circumstances a packing list and other personal details such as passport, flight ticket, work permit or visa may be required to satisfy customs.
Do take into account that some countries do not offer duty free clearance.
It is the sender’s responsibility to ensure that you are aware of your own personal circumstances, what you are sending and the prevailing customs regulations of the destination country will affect the categorisation of your shipment and consequently whether you will be liable to pay customs duties, taxes or local charges.
If your item is stopped by a customs authority and it is assessed as not complying with duty free entry, it will be the responsibility of the recipient to complete any clearance procedure, and pay any duties, taxes or charges. In some rare cases you may be required to present a passport at a local office, or if a customs authority has removed the item from your shipment you may also be required to pay the authority an additional delivery fee or to collect/destroy the item.