The IPO is expected to be one of the biggest in recent times, with an estimated size of over Rs 10,000 crore, merchant banking sources said.
NSE's IPO is being keenly awaited in the market as one of the biggest in recent times. Rival BSE got listed in February.
The regulatory officials said the exchange will have to file fresh papers as issues related to co-location case have held up regulatory go-ahead for its earlier proposal and Sebi wants greater disclosure about the matter in the draft red herring prospectus (DRHP).
When contacted, an NSE spokesperson told PTI: "We had informed shareholders that DRHP will remain open and we will refile it once we get clarity on the co-location matter".
The co-location case relates to some brokers allegedly getting preferential access in the high frequency trading system at NSE's servers during 2011-14.
Widening the investigation into the high profile case, the government is likely to bring in the SFIO (serious fraud investigation office) to delve into possible violations of corporate law while Sebi may issue show cause notices to many more entities including brokers, officials said.
Sebi had previously issued notices to 14 individuals and entities and the scope of probe has widened considerably since then amid concerns of possible illicit fund flows involving certain market entities, according to official sources.
While the government is keeping a close tab on the developments related to the case, multiple agencies, including the Income Tax Department, are moving ahead with their respective probes.