Customs procedures vary depending on the receiver country and the carrier you choose for the transport of your goods.
Some carriers support digital/electronic submission of customs declarations, while others require physical invoices and customs declarations attached on the outside of the shipment.
When using Shipmondo, you'll be informed during the booking process wether physical invoice and customs declaration are required. Otherwise we make sure that all the customs information, that you've entered, is submitted to the carrier electronically.
This will be done by automatically creating customs documents, alongside your freight label, in case this is necessary. Put all copies of the printed customs documents into a plastic pocket and attach on the outside of the package so that they are visible to customs staff.