The banks leading preparations for the listing were Goldman Sachs, JPMorgan Chase, Mizuho Financial Group and Morgan Stanley, the sources said.
The PayPay offering may raise more than US$2 billion from investors when it takes place, which the sources said could be as soon as the final quarter of this year.
The sources declined to be named as the information was not public and cautioned that factors including timing and the amount the IPO could raise are subject to market conditions.
SoftBank, Goldman Sachs, JPMorgan, Mizuho and Morgan Stanley declined to comment.
PayPay played a role in encouraging Japanese consumers to move away from a long-standing preference for cash by offering rebates on payments through its mobile app.