Investigating judges suspect senior FN officials and associated companies defrauded the state by inflating campaign expenses for the 2012 legislative elections.
"We are innocent of all the accusations against us," said party treasurer Wallerand de Saint-Just.
A "micro-party", named Jeanne, is suspected of having received illicit financing from an events company, which has already been charged along with six other people in the probe.
The charges against the FN come three months before regional elections seen as a litmus test ahead of 2017 presidential polls.
The party remains on top of opinion polls despite its legal woes and a bitter family feud in which leader Marine Le Pen ousted her father and party founder Jean-Marie Le Pen over a string of controversial remarks.
While the FN remains anti-EU and anti-immigration it has worked hard to soften its image since Marine took over in 2011 and has seen its popularity soar, enjoying a series of election successes.
Several polls have shown she could pose a serious challenge to the conservative Republicans of former president Nicolas Sarkozy as well as the ruling Socialists in 2017.
The FN is also under investigation by the European Parliament for suspected fraud totalling 7.5 million euros ($8.1 million) over salaries paid to EU parliamentary assistants.