Buy-back regulation: phased elimination of open-market buy-backs and mandatory book-building, electronic filings and procedural limits. Amendments update buy-back regulation by defining frequently traded shares and secretarial auditor, requiring thresholds to be based on standalone or consolidated statements whichever is lower, phasing out open-market buy-backs with transitional caps, mandating electronic filings and merchant banker certifications, broadening acceptable escrow instruments, and introducing a book-building process with specified disclosure, pricing, retail participation limits and a prohibition on promoter participation in book-building.