The block deal on Friday could be at a base price of 440 rupees per share, CNBC-TV18 said in a tweet. PB Fintech's shares closed at 461 rupees on Thursday.
SoftBank declined to comment, while PB Fintech did not immediately respond to a Reuters request for comment.
Japanese conglomerate SoftBank owns a more than 10% stake in PB Fintech through two of its units, according to exchange data.
One of the units, SVF India Holdings, will likely sell the shares, the CNBC-TV18 tweet said.
(Reporting by Rama Venkat in Bengaluru; Editing by Devika Syamnath)