Investigators suspect the FN used money from Brussels earmarked for parliamentary assistants to pay staff to work for the party in France.
Other European parliamentarians, including Le Pen's father Jean-Marie Le Pen and her companion Louis Aliot, have also been on the radar of the European investigative body OLAF for allegedly misusing parliamentary aides' wages.
The case was triggered by a complaint from the European parliament, which accused the Front National of defrauding it on a large scale.
During the Presidential election Marine Le Pen made inroads with white conservative gay voters by playing off concerns about Islamic extremism - despite pledging to repeal the country's 2013 same-sex marriage law. If the judges send Ms Le Pen to trial at the end of their probe, she could face up to three years in prison and a fine of up to €375,000 (S$590,000) if convicted.
Ms Le Pen, 48, has also denied any wrongdoing and has said the case is politically motivated.
Marine Le Pen formally investigated in EU funding inquiry
In March, French investigators raided the party's headquarters outside Paris in order to find out if the European Parliament funding for MEP assistance had been abused with fake jobs.
Le Pen denies the charges.
Those pictures saw her placed under investigation for the "dissemination of violent images".
"There is nothing illegal", Florian Philippot, the party's vice president, said.
Le Pen's lawyer, Rodolphe Bosselut, said she had been summoned by investigating magistrates in Paris and that they had, "as expected, charged her", adding that she would appeal. She had however promised to cooperate with the investigation after the May presidential and June parliamentary elections were over.
What you need to know to combat cyber attacks
Kaspersky said the "NotPetya" attack had hit 2,000 users in Russia, Ukraine , Poland, France, Italy, the UK, Germany and the US. The global cyberattack is similar to a recent WannacCry ransomware that crippled over 300,000 computers worldwide.