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

The National Elections Act (CAP 343)2010

Article 111(2)The Registrar shall not fix a date forhearing of any election petition unless the petition has paid into court, assecurity for costs, an amount not exceeding five million shillings in respectof each respondent 3)The petitioner shall within fourteen days after filing apetition, make an application for determination of the amount payable assecurity for costs, and the court shall determine such application within thenext fourteen days following the date of filing an application fordetermination  of the amount payable assecurity for costs

http://www.unisa.ac.za/contents/faculties/law/docs/National_Elections_Act-.pdf

The National Elections Act providesunder  chapter VII Article 117(1) Thechief Justice may make rules of the court regulating the procedure and practiceto be followed and prescribing the fees to be paid and in relation to petitionsand applications under this Chapter