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

ELECTIONSDECREE, (DECREE 78 OF 1996)

Presentation of election petition

Article 98.

[…]

(2) At the time of the presentation of the petition, or within threedays afterwards, the petitioner shall give security for the payment of allcost, charges and expenses that may become payable by him to any witnesssummoned on his behalf or to any respondent any witness summoned on his behalfor to any respondent.

(3) The security shall be such amount and shall be given in such manneras the Court may order, and in the event of failure to comply with such orderno further proceedings shall be had on the petition.

http://www.iec.gm/files/images/Elections_Decree_78_of_1996.pdf