Mumbai, Aug. 15 -- The National Stock Exchange (NSE), the country's largest stock bourse, aims to launch its initial public offering (IPO) by mid-September and is eyeing a possible listing by September 25, three people with knowledge of the company's plans said. "The bourse is targeting the IPO launch around the beginning of Ganesh Chaturthi, in the middle of next month," the first person said. The second person told Mint that regulatory approval is expected "anytime now", following an addendum filed by the exchange on August 6. The timing coincides with the auspicious festival of Ganesh Chaturthi, which runs for 10 days starting September 14. NSE managing director and CEO Ashishkumar Chauhan is known to be an ardent devotee of Lord Ganesha. According to NSE's update to its offer document filed with Sebi, SBI Capital Markets will join parent State Bank of India to jointly offer 24.75 million shares in the issue. In the original draft prospectus filed in June, SBI was listed as the sole selling shareholder. "Because of the addendum, the Sebi observation letter, which was expected earlier, is now likely to be issued anytime this month," the second person added. An observation letter from Sebi signifies regulatory approval of a company's draft IPO papers, clearing the path for the offering to proceed. An NSE spokesperson said in response to Mint's emailed queries, "The company has filed a DRHP with Sebi. We are unable to provide further comment at this stage." The company is likely to begin its final roadshows for price discovery next week, the third person cited above said. "Global marketing is now done and the bankers are likely to approach investors with the final pricing and seek guidance," he added. While the roadshows target institutional investors and high-net-worth individuals, the outreach for retail investors will begin next month after the company files its Red Herring Prospectus with the Registrar of Companies (RoC). In June, NSE filed its draft red herring prospectus with the market regulator for what could be one of the biggest-ever IPOs in India. In one of the largest secondary market transactions via an offer for sale (OFS), existing shareholders will offload 148.9 million shares, representing a 6% stake in NSE. An OFS involves existing shareholders getting a partial or complete exit from a company, with no funds flowing to the debuting company. The country's largest stock exchange had a 93.1% market share in the equity cash segment at the end of June, with smaller rival BSE accounting for the rest, according to exchange data. In equity options, which is the the key revenue generator for both bourses, NSE enjoyed a market share of 69.4% at the end of June, with BSE accounting for the rest....