Is there a legally mandated filing fee and/or deposit?

• Ley Orgánica 5/1985, de 19 de junio, del Régimen Electoral General.
• In effect since 21/06/1985 (last update in force since 08/09/2011)

http://www.infoelectoral.mir.es/Normativa/loreg_2011.htm

Artículociento diecisiete

Losrecursos judiciales previstos en esta Ley son gratuitos. No obstante proceder?la condena en costas a la parte o partes que hayan mantenido posicionesinfundadas, salvo que circunstancias excepcionales, valoradas en la resoluci?nque se dicte, motiven su no imposici?n.

Article 117

Judicial appeals providedin this Law are free. This not wtihstanding, the costs of the proceedings willcorrespond to the party or parties who had maintained baseless positions,unless there were exceptional circumstances, to be assessed in the judicialdecision, that had motivated not to impose those costs.