The Dutch Central Authority (Centrum IKO) is the first organisation to talk to if you want to file a return request yourself without starting a court procedure yet. They will do some research before deciding if they will accept your request. And then they will start the out of court procedure, which will not cost you anything.
They will contact the parent who took the child to the Netherlands and see if he or she is willing to cooperate or to cooperate with mediation.
If that does not have any positive result within weeks, you will have to decide wether or not you wish to start a court procedure. Unfortunately, the Central Authority will not pay the costs of the procedure for you.
The Hague Child Abduction Convention aims to ensure the immediate return of children who have been unlawfully transferred or detained in a Contracting State. The treaty serves to protect the children, but also to protect existing rights of access.
The procedure in which the court is requested to order the return of the child is conducted in the country where the child is currently residing. That court must determine the habitual residence of a child. The country where it previously lived, or the country where it now resides?
The Dutch Central Authority can also help you when you are worried that your child is about to be abducted from The Netherlands to another State.