More than €4 million was spent by the 44 candidates and seven political parties who contested June's European election.
The biggest spenders were Fianna Fáil candidates, with costs totalling almost €1,300,000. Fine Gael candidates spent just over €1,100,000, while the Labour party spent €715,431.
Sinn Féin candidates spent €314,000, the Green Party's candidates spent €200,000 and the Socialist Party's total was €28,308.
The highest figure spent on an individual was invested in successful Fine Gael candidate Ms Mairead McGuinness, whose campaign cost €225,139. The East constituency candidate got one of the highest votes of the election nationwide.
The second-highest amount was spent on her party colleague Mr Gay Mitchell, whose Dublin campaign cost only €2,000 less.
The figures, disclosed by the Standards in Public Office Commission (SIPO), reveal that of the independent candidates, Galway-based Mr Marian Harkin spent the most, forking out €87,691.
Former Dublin mayor Mr Royston Brady, who failed to get elected, accepted the largest amount in donations, totalling €40,713. His campaign cost almost €200,000, the fifth-highest of all 44 candidates.
Disability rights campaigner Ms Kathy Sinnott spent the least of all successful candidates - almost €48,000.
The Standards in Public Office Commission reveals that more than €121,000 was donated to unsuccessful candidates overall.
All elected candidates and those who achieved one-quarter of the quota are eligible for reimbursement of election expenses. Of 27, all but one qualify for the maximum reimbursement of just over €38,000.
The Exchequer will make the refunds, which total more than €1 million.
The SIPO disclosed it had written to the Garda asking it to investigate the failure of the independent candidate Mr Gerard Hannan to furnish a donation statement. The SIPO said that at the time of going to print with today's report, it had not received a donation statement from Mr Hannan.
SIPO also wrote to the Garda in September in relation to the failure of the election agent for Ms Madeleine Taylor Quinn (FG) to furnish an election expenses statement. However, the statement was eventually furnished to SIPO on October 27th.
Additional reporting: PA