In a signed article in Le Monde, Chirac said his decision to answer the judge's questions was "perfectly normal and in keeping with the conception I have always had of the principles of the Republic."
In the article, Chirac conceded that all political parties turned a blind eye to financing irregularities in the 1980s and early 1990s, but he said this needed to be seen in the context of the time.
The so-called "fake jobs" investigation involves allegations that members of his Rally for the Republic (RPR) party had their salaries paid by Paris City Hall or by private companies that won contracts there.
Alain Juppe, a former prime minister and a close ally of Chirac, was convicted in the affair in 2004, and banned from politics for a year.
Chirac, whose presidency ended in May, was mayor of Paris from 1977 to 1995. Three other RPR party finance investigations from the period, into which he could also be drawn, remain open.
Chirac has consistently denied any wrongdoing.
Last month his lawyer, Jean Veil, said Chirac would "answer all questions in all the cases that may concern him" in investigations relating to events before he took over as president.
However he said that Chirac refused to be interviewed in the investigation into the so-called Clearstream scandal, which took place when he was in office.
The Clearstream investigation involves allegations that Nicolas Sarkozy, then the interior minister and now president, was the victim of a smear campaign in 2004 aimed at derailing his bid for the presidency.
Dominique de Villepin, a former prime minister, is to be questioned next week in the affair, amid reports that he will be placed under judicial investigation, a first step towards possible libel charges.
Chirac has also been implicated in the investigation, but his lawyer said that in this matter he remains protected by presidential immunity.