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

• Representation of the People Act 1983

Art. 136 Security for costs.

(1) At the time of presenting anelection petition or within three days afterwards the petitioner shall givesecurity for all costs which may become payable by him to any witnesssummoned on his behalf or to any respondent.

(2) The security shall be (a) inthe case of a parliamentary election petition, such amount not exceeding ?5,000as the High Court or a judge of the High Court, directs on an application madeby the petitioner; and

(…) shall be given in theprescribed manner by recognisance entered into by any number of sureties notexceeding four or by a deposit of money, or partly in one way and partly in theother; 

PLUS

Art 154. Costs of petition.

(1) All costs of and incidental to the presentationof an election petition and the proceedings consequent on it, except such asare by this Act otherwise provided for, shall be defrayed by the parties to thepetition in such manner and in such proportions as the election court or HighCourt may determine.

(2) In particular (a) any costs which in theopinion of the election court or High Court have been caused by vexatiousconduct, unfounded allegations or unfounded objections on the part either ofthe petitioner or of the respondent, and (b) any needless expense incurred orcaused on the part of the petitioner or respondent, may be ordered to be defrayedby the parties by whom it has been incurred or caused whether or not they areon the whole successful.

(3) In the application of this section to Scotland,references to the High Court shall be omitted in relation to an election ofcouncillors.