A complaint has been registered with the Income Tax investigations wing against Kumaraswamy.
The complaint acknowledged by the department accused the former chief minister and former prime minister H D Deve Gowda's family of indulging in money laundering case.
The IT department also questioned the various investments made by his family members in India and countries abroad.
The complaint has 600 pages annexure details the allegations with specifics.
Reportedly, last week Kumaraswamy appeared before a Lokayukta Special Investigation Team after he was issued a notice to appear in connection with the Janthakal case.
On March 29, the Supreme Court asked the Special Investigating Team of the Karnataka Police to probe allegations against two former chief ministers N Dharam Singh and H D Kumaraswamy in connection with an iron ore mining case.
The apex court, however, granted relief to former chief minister, S M Krishna in the case.
The apex court also stayed all High Court proceedings and asked all not to pass any order on it.
This has been another trouble to Kumaraswamy after illegal mining case summons.