Le Pen, a former member of the European Parliament, was charged with breach of trust for allegedly placing her chief of staff and her body guard on the EU payroll between 2009 and 2016.
The National Front has denied the allegations.
The allegations originate with the European Parliament which alleges that Le Pen and other Front National MEPs spent £4 million on assistants since 2012 that were doing party work in France and not assisting MEPs in the European Parliament as the party claims.
Earlier this year, in April, it was reported that the EU Parliament believed fake jobs involving Marine Le Pen's National Front party had cost the institution almost Euro 5 million (USD 5.5 million).
The case was brought as a result of a complaint from the European parliament which accused FN of defrauding it on a large scale.
Later the cost was estimated at Euro 1.9 million but the new estimate cited by police sources is more than twice as high - Euro 4,978,122.
Instead, investigators say this money was used to pay for staffers working for Le Pen's National Front.
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Ms Le Pen had refused to answer questions on the matter during the campaign but said she would co-operate after the final round of presidential election voting. She will also seek a suspension of the investigation.
Le Pen's chief of staff Catherine Griset was put under formal investigation on February 22 after a day of questioning over the alleged misuse of European Union funds to pay parliamentary assistants.
The leader of the National Front who gave French President Emmannuel Macron a run for his money earlier this year is now being investigated concerning potentially fraudulent use of government funds.
Le Pen denies the charges.
The French judiciary has already requested that the European Parliament lift Le Pen's immunity.
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 was also charged with complicity of breach of trust for her wider role as head of the party. A conviction for breach of trust charge carries a potential penalty of up to three years in prison and a fine of 375,000 euros ($428,000).
Le Pen was first elected to the European Parliament in 2004.
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