How to pay the customs duties?

To find out if a package is blocked in customs, you should go to the website of the carrier responsible for the delivery of your order using the tracking number associated with your package. 

The customs duties are to be paid directly to the carrier in charge of the delivery. Payment can usually be made online on the carrier's dedicated portal or by bank transfer. For more information, please contact the carrier in charge of the delivery of your package.

It should be noted that no customs fees should apply when transporting goods from one EU country to another. Similarly, no customs documents are required when shipping goods from one EU country to another.