Paytm did not officially disclose details of the funding, but a source said the Indian company raised $1 billion in the latest round.
SoftBank's fresh investment in Paytm comes as the Japanese investment firm's founder Masayoshi Son battles to restore his reputation after an ill-fated investment in office-sharing firm WeWork.
New investment deals by SoftBank are also under growing scrutiny after the group reported its first quarterly loss in 14 years, dragged down by an $8.9 billion hit at Vision Fund.
Paytm said on Monday it will expand into insurance, lending, stockbroking and investments and invest 100 billion rupees ($1.4 billion) over the next three years to bring in more users to its services.
"This new investment by our current and new investors is a reaffirmation of our commitment to serve Indians with new-age financial services," Paytm founder and chief executive Vijay Shekhar Sharma said in the statement.
Other investors include Discovery Capital and funds advised by T. Rowe Price Associates.
(Reporting by Sankalp Phartiyal in New Delhi and Derek Francis in Bengaluru; Editing by Sherry Jacob-Phillips & Shri Navaratnam)
