Sinn Féin and the DUP spent around €115,000 each on contesting last December’s general election, the Electoral Commission said.
The DUP won eight seats and Sinn Féin seven.
North Belfast MP Nigel Dodds was the unionist party’s most high-profile casualty as he was toppled by murdered solicitor Pat Finucane’s son John.
Sinn Féin spent €110,017, almost all accounted for by donations to candidates, data from the Electoral Commission showed.
The party spent €40,411 on unsolicited material sent to electors like leaflets.
The DUP spent €120,530.
A total of €85,760 involved donations to candidates.
The party spent €87,871 on unsolicited material sent to electors like leaflets.
Following the poll the DUP lost two MPs including its Westminster leader Mr Dodds.
Mr Dodds was a high-profile supporter of Brexit and Sinn Féin labelled him the “architect” of a process which was deeply unpopular amongst many nationalists.
Emma Little-Pengelly was defeated by Claire Hanna of the SDLP in South Belfast.
SDLP leader Colum Eastwood won Foyle with a massive majority.
The cross-community Alliance Party made gains and took the North Down seat.
The DUP’s Alex Easton had hoped to win the seat but lost out to Alliance deputy leader Stephen Farry.
The DUP and Sinn Féin saw their share of the vote drop significantly compared with the 2017 general election, by 5.4% and 6.7% respectively.
They reopened negotiations on Stormont powersharing immediately after the election and that led to a resurrection of the devolved institutions in January.