Law 39/2015:
Article 44. Unsuccessful notification.
"When those interested in a proceeding are unknown, the place of service is ignored, or, after such service has been attempted, it has not been possible to serve, service must be given by means of a published notice in the "Official Gazette of the State".
Likewise, previously and on an optional basis, the administrations can publish an announcement in the official bulletin of the autonomous community or province, on the notice board of the City Council of the last address of the person concerned or of the consulate or section consular of the corresponding embassy.
Public administrations can establish other complementary forms of notification through the rest of the media, which do not exclude the obligation to publish the corresponding announcement in the "Official State Gazette".
Article 45. Publication.
"4. Without prejudice to the provisions of article 44, the publication of acts and communications that, by legal or regulatory provision must be practiced on a notice board or edicts, is understood to be completed by their publication in corresponding official newspaper."
Third additional provision. Notification by means of an announcement published in the "Official Gazette of the State".
"1. The "Official Gazette of the State" must make available to the various public administrations an automated system of transmission and telematic management to publish the notification announcements provided for in article 44 of this Law and in this additional provision. This system, which must comply with the provisions of this Law and its implementing regulations, must guarantee the speed of publication and its correct and faithful insertion, as well as the identification of the sending body.
2. In the administrative procedures that have specific regulations, if the cases provided for in article 44 of this Law occur, the practice of notification must be done, in any case, by means of an announcement published in the "Bulletin Official of the State", without prejudice to the fact that previously and with an optional nature it can be done in the manner provided for by the specific regulations mentioned.
3. The publication in the "Official Gazette of the State" of the announcements referred to in the two previous paragraphs must be made without any financial consideration by those who have requested it."