Mrs. Gandhi was summoned earlier but the questioning had been deferred, after she tested positive for COVID-19 and was subsequently hospitalized.
After being released from hospital, she had asked for more time to appear before the agency.
Congress leaders met on Wednesday evening to discuss holding protests, as Mrs. Gandhi is expected to appear at the ED office at 11 am today.
All India Congress Committee office bearers will accompany her in a mark of solidarity, sources said.
Party MPs will also join in, after parliament adjourns. State units of the Congress party are also planning to hold protest across the country.
The party had earlier held protests when former party chief Rahul Gandhi, was questioned by the ED, in connection with the same case.
Mr Gandhi had undergone questioning by the ED for five days, as party leaders held foot marches and sit-down protests, with many senior leaders being detained. Protests continued at Jantar Mantar in the capital.
The ED has also questioned senior Congress leaders Mallikarjun Kharge and Pawan Bansal in the investigation, which involves the Young Indian’s takeover of AJL (Associated Journals Limited), the company which ran the National Herald newspaper.