When should a declaration be filed?

Are you entering or leaving the EU with € 10,000 or more in liquid assets? In that case, you are required to file a declaration with Dutch Customs if you:

are not arriving directly from one of these countries or regions, or
are nog travelling directly from the Netherlands to one of these countries or regions.

EU countries and territories for rules about bringing money across the border

EU countries and territories for rules about bringing money across the border are:

Austria
Belgium
Bulgaria
Czech Republic
Cyprus
Denmark
Estonia
Finland
France (Including the French overseas departments Martinique, Guadeloupe, Guyana, Réunion and Mayotte and Saint-Martin)
Germany
Greece
Hungary
Ireland
Italy
Latvia
Lithuania
Luxembourg
Malta
The Netherlands
Poland
Portugal (Including the Azores and Madeira)
Rumania
Slovakia
Slovenia
Spain (Including the Canary Islands (Lanzarote, Fuerteventura, Gran Canaria, Tenerife, Gomera, Hierro and La Palma), the Balearic Islands (Mallorca, Menorca, Formentera and Ibiza) and Ceuta and Melila)
Sweden