Are you entering the Netherlands and bringing goods with you? This is governed by certain rules. An important aspect of this is the country where you were immediately before travelling to the Netherlands. Are you travelling from the Netherlands to a different country, or will you be entering the Netherlands in transit? There are rules governing this, too.
I’m travelling from another EU country to the Netherlands
Goods and services have freedom of movement within the European Union (EU). You will not pass Customs and are not required to make declarations. But there are exceptions for excisable goods, currency, monetary instruments, cars, motorcycles, trailers, animals and a number of other specific products.
I am travelling from a non-EU country to the Netherlands or the EU
Are you entering the Netherlands from a non-EU country? If so you are only permitted to bring a limited quantity of goods with you without being liable for import duties. Are you bringing more goods with you? If so you must declare them (verbally) to Customs (red channel). There are some goods that you are only permitted to bring with you if you have a permit. And there are also some goods that are not permitted to take to the Netherlands at all.
I am departing from the Netherlands and taking goods with me
You are exciting the Netherlands. In that case you are subject to rules for certain goods.
Customs green and red channel
At airports and seaports there are 2 customs channels. A red channel for if you have something to declare and a green one for if you have nothing to declare.
Obligation to cooperate with customs inspection
Are you entering or exiting the Netherlands? If so, Customs can inspect your baggage both in the 'red channel' and the 'green channel'.
Are you arriving in the European Union (EU) by air and taking another flight to travel directly to another EU member State? If so, you only need to declare your hand luggage in the first EU country in which you arrive.