Underwriting rules require lead managers and syndicate members to contractually cover under subscription in IDR public offers. Regulation 198 requires that issuers of IDRs seeking underwriting appoint merchant bankers or registered stock brokers for non book built IPOs; for book built public issues underwriting must be by lead managers and syndicate members, with a pre prospectus underwriting agreement specifying subscription commitments at a predetermined price, lead managers covering unmet syndicate obligations, subscription limited to underwriting fulfilment, and lead managers meeting minimum underwriting thresholds per Merchant Bankers Regulations, 1992, at least to the extent of minimum subscription.