Customs declaration is the collective term for declaration at the customs in each direction of transport, such as Export declaration for the export of goods or import declaration when importing goods.
For the export declaration there is a threshold above which the customs declaration shall be made, which means a duty on the customs declaration is at least 1000 € value or 1000 kg. (See also export declaration).
Upon importation, the customs declaration is already mandatory from a tax rate of 10.00 €. The customs declaration may be lodged in advance, that means, before the goods physically arrive. The requirement to submit the customs declaration is made at the latest when the goods arrive within the EU.