The declaration concerning the acceptance or waiver of the succession or the declaration designed to accept and limit the liability for the deceased’s debts, shall be valid as to the form where it meets the requirements of the law applicable to the succession, and also when it is made according to the law of the State in which the person making the declaration has his habitual residence.

If the law of the member State of the residence of the beneficiary rules that this declaration must be made before a court, the court will have jurisdiction to receive the declaration, even though it does not have the jurisdiction to rule on the succession as a whole.

You can find more information at international inheritance in Spain