Besides the IT department, Vadra is being investigated by the Enforcement Department under the provisions of PMLA pertaining to allegations of money laundering in the purchase of a London-based property worth 1.9 million pound.
The deadline for companies and individuals who need to get their accounts audited too have been extended by 15 days till February 15.
The questioning which began at the ED sub-zonal office in Kozhikode at 10 am on Tuesday got over late in the night.
Though direct checks have been completed, detailed examination of the documents would continue and this would take about two months.
The further extension for filing tax returns has been given in view of the challenges faced by taxpayers in meeting the statutory and regulatory compliances due to the outbreak of COVID-19.
The deadlines have been extended by one month to three months. The fees and penalties for late returns have either been reduced or waived.
The decision has come in the wake of many taxpayers facing difficulty in filing their income tax returns due to the outbreak of Covid-19 pandemic.
Trump, who has fiercely guarded his tax filings and is the only president in modern times not to make them public, paid no federal income taxes in 10 of the past 15 years.
Launching the platform 'Transparent Taxation Honoring the Honest', Modi said the department will start faceless appeals from September 25.
This is the third extension given by the government for taxpayers to file both original and revised tax returns for 2018-19 fiscal.