Opposition parties filed an urgent application in the electoral court on Thursday over their demand that IEC chairperson Pansy Tlakula must resign, UDM leader Bantu Holomisa said.
"The papers have been served with the Electoral Court at 3.15pm this afternoon according to our lawyers," he said.
"Everything from the side of the opposition parties was finalised earlier and we signed the documents."
Holomisa said he did not have more information at the time.
Opposition parties had given Tlakula until the close of business on Monday to respond to their call for her to step down.
On Tuesday, Holomisa said she had not responded to them, which showed "how arrogant" she was.
Earlier this month, the parties said they were worried about the credibility of the May 7 elections. The parties met IEC management.
Parties calling for her resignation were the United Democratic Movement, the African Christian Democratic Party, the Congress of the People, Agang SA and the Economic Freedom Fighters.
The Inkatha Freedom Party was originally named on the list of opposition parties but on Monday it said it was not part of the group.
The Azanian People's Organisation and the United Christian Democratic Party were also initially part of the group but were not listed as applicants on the court papers.
Agang SA and the EFF had both indicated on Monday that they were still supporting the call for Tlakula to resign.
Last month, a forensic investigation by auditors PriceWaterhouseCoopers on behalf of the national treasury on the procurement of the IEC's Riverside Office Park building in Centurion, Pretoria found that the process was neither fair, transparent, or cost-effective.
It also found that Tlakula did not give guidance or formally inform various people what was expected of them in the process.
Tlakula has maintained that the report did not accuse her of corruption. The treasury report followed a recommendation from public protector Thuli Madonsela in her own report into the matter, released in August 2013.
Madonsela found Tlakula had played a "grossly irregular" role in procuring the premises. She recommended that Parliament consider taking action against Tlakula. The complaint against Tlakula to Madonsela was lodged by Holomisa. Tlakula was chief executive at the time the complaint was lodged.
The ANC on Tuesday said the call for Tlakula to resign was not genuine and based on the desire by some parties to delegitimise the elections. – Sapa