The leftist ex-president, 63, has rejected the accusations that she was involved in suspect currency transactions by Argentina's central bank last year in the closing months of her presidency as a plot by the new government.
"I am not afraid of them," she wrote in a declaration filed with the court on Wednesday and published on her Facebook page.
"I will face up to this case and any other one that they want to fabricate against me."
Macri took over from Kirchner in December after he narrowly beat her side in an election. That ended 12 years of leftist rule by her and her late husband Nestor, who came to power after a financial crisis.
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Macri launched steps to liberalize the Argentine economy, Latin America's third biggest. Kirchner's supporters say his spending cuts and price rises are hurting poorer families.
Thousands of Kirchner's supporters gathered in the rain to greet her as she arrived smiling at the courthouse in central Buenos Aires.
"If you go to jail, I'm going with you," read one of the signs waving in the crowd.
Judge Claudio Bonadio is investigating whether there are grounds to charge Kirchner over claims that she mishandled public funds in connection with the sale of dollars below market value by the central bank in September.
It is one of numerous cases connected to former leading officials from the Kirchners' center-left governments.
Bonadio is an open critic of Kirchner, who in the past tried to have him dismissed from his post.
She arrived in Buenos Aires yesterday following four months in southern Patagonia, where she secluded herself after leaving office.
Argentina's former economy minister and former central bank chairman are also named in the case.
News reports over the weekend said Kirchner could also be investigated for alleged money laundering in a separate suit fanned by revelations from the Panama Papers leaks.