No. To be enforceable against third parties, the renunciation of an inheritance must be formalized with the judicial court of the last domicile of the deceased, by filing or sending a simple letter which is duly completed, Cerfa 15828*05 form. One must also attach a full copy of the death certificate of the deceased, a full copy dating back less than 3 months of the birth certificate of the person renouncing as well as a copy of both sides of their proof of identity. It is also possible to file or send this request to a notary.
Subsequently, the renouncer will receive a receipt for this waiver by a simple letter, which must be kept in order to justify this process with regard to the creditors of the succession.