In principle, the child and the legal representatives (usually the mother and father) must agree to an adoption.

If the children are younger than 14 years old, only the legal representatives can consent (usually the mother and father).

If the child is older than 14, the child must also consent to the adoption.

If a court has not yet ruled on the adoption, a child aged 14 or older can revoke the adoption. This is called revoking consent to the adoption.

This revocation is also possible if the legal representative has consented to the adoption and the child later turns 14. However, this is only possible if the adoption has not yet been finalized (i.e. no court has yet ruled on the adoption).

The child can revoke the adoption on their own. It does not need permission to do so. It does not matter why the child wants to revoke the adoption.
A form is prescribed for the revocation. The revocation must be "publicly notarized". The child can do this at a youth welfare office or at a notary's office.
The notarization does not cost any money at the youth welfare office. At a notary's office, notarization costs money.