The long-awaited initial public offering (IPO) of the National Stock Exchange (NSE) is set to move a step closer, with the country's largest stock exchange expected to file its preliminary papers with Sebi next week, people aware of the matter said. This comes after NSE's board approved the proposed IPO on February 6, following receipt of Sebi's no-objection certificate (NOC). The public issue will be entirely an offer for sale (OFS), with no fresh issue component.