The nearly Rs 30,000-crore initial public offering (IPO) of the National Stock Exchange is likely to open for public subscription on September 18, and list on September 25, sources said on Tuesday.The price band for the IPO was expected to be announced on September 15, followed by the anchor book on September 17, they said. The public issue is likely to remain open on September 18, September 21 and September 22. There is no official announcement on this issue calendar by the bourse.The issue, which could raise around Rs 30,000 crore, is set to surpass Hyundai Motor India’s Rs 27,870-crore offering in 2024 to become India’s largest IPO, the sources said.The IPO will comprise an offer for sale (OFS) of up to 148.9 million equity shares of face value Re 1 each, representing nearly 6 per cent of NSE’s paid-up equity capital.