50. Do third parties have to report on election campaign finances?

Electoral Act 1997 Section 36.
—(1) (a) The national agent of a political party, the election agent of a candidate and every person who incurs election expenses under section 31 (7) shall, within the fifty six days next following the polling day at an election, furnish to the Public Offices Commission a statement in writing of all election expenses (whether paid or not) incurred by such agent or person in relation to the election and the several matters to which such expenses relate, together with all relevant vouchers. (b) The national agent of a political party shall include in the statement of election expenses furnished by him or her under paragraph (a): (i) details of the election expenses incurred by the said agent pursuant to section 32 (1) (b) or 33 (1)(b), as may be appropriate; (ii) the name of each candidate whose candidature was authenticated by the party at that election and in respect of whom election expenses are deemed to have been incurred by the said agent under section 32 (1)(b)(ii) or 33 (1)(b)(ii), as may be appropriate, and the constituency in which each such candidate was a candidate at the election; and (iii) the amount of election expenses (if any) agreed in writing pursuant to section 32 (1)(b)(i) or 33 (1)(b)(i), as may be appropriate, between the party and each such candidate and the amount of election expenses incurred by the said agent pursuant to section 32 (1)(b)(i) or 33 (1)(b)(i), as may be appropriate, in respect of each such candidate. (c) The election agent of a candidate whose candidature was authenticated by a political party at the election shall include in the statement of election expenses furnished by him or her under paragraph (a) the amount of election expenses agreed in writing pursuant to section 32 (1)(b)(i) or 33 (1)(b)(i), as may be appropriate, between the candidate and such party.

"Third parties are subject to the same rules as candidates, agents, and parties in relation to the reporting of electoral expenses.  The following must be included on the election expenses statement completed by the third party/other person: details of all expenses incurred and payments made by the third party/other person; details of any disputed claims ; details of any late claims for payment (i.e. claims received more than 45 days after polling day which must not be paid)." 
See Standards in Public Office Commission. 2020.  Guidelines for the General Election to the 33rd Dáil 8 February 2020 [National Agents, Third Parties, Other Persons and Publishers], p. 21.