Neither ASIC nor Prospa has said which loan terms are being looked at by ASIC.

An ASIC spokesman reiterated that it had been carrying out a review of small business loan contracts on Thursday. "It's a matter for the company and the ASX as to when and how it lists," the spokesman said.

Market sources who did not want to be named said the company faced a dilemma because proceeding with the float could lead to a sharp fall in its share price, or raise concerns about whether investors had been fully informed through the prospectus.

The decision to postpone the float again, however, could also damage investor confidence in the deal, harming its IPO prospects.

Prospa and its joint lead managers - investment banks UBS and Macquarie - said the 48-hour delay was because it was "seeking to clarify queries raised by ASIC yesterday in relation to Prospa’s small business loan terms," as part of a wider review.

However, ASIC has suggested the review is not new, and Kate Carnell, the Australian Small Business and Family Enterprise Ombudsman, said she had raised the question of Prospa's compliance with unfair contract laws "very consistently" in her consultation with fintech lenders. Ms Carnell said ASIC's queries in this area were "quite generic."

"Prospa is acutely aware of it [unfair contract legislation], it's just now ASIC is saying can you please show us how you're complying,'' Ms Carnell said.

One fund manager, who was not participating in the float because they thought the valuation too expensive, predicted investors who had been allocated stock would have an argument for a supplementary prospectus being issued.

"This is an IPO of a new company in a new space," the investor said.

A fintech industry source said they were "blown away" that Prospa may not have dealt with all ASIC addressed unfair contract terms legislation, and said the episode was damaging for the whole industry.

Key investors in Prospa include London-based venture capital firm Entree Capital, which has a 34 per cent stake in the business, and the co-founders and joint chief executives Greg Moshal and Beau Bertoli.

Prospa's plan has been to float with a market capitalisation of $576 million, of which $146 million was to be raised in the initial public offering.