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

http://www.irishstatutebook.ie/1992/en/act/pub/0023/print.html#sec21

The Electoral Act 1992

PART XXI

D?il Election Petitions

132.— (3) (a) Subject to paragraph(b) and Rule 2 (2) of the Third Schedule a petition shall not be accepted for lodgementwith the court unless the petitioner lodges with the petition security in thesum of ?5,000 for costs which may become payable by him.