Underwriting obligations: book runners and syndicate members must underwrite and only subscribe to fulfil underwriting commitments. Regulation 13 requires underwriters for public issues and rights issues to be appointed per underwriter regulations; book-built issues are underwritten by book runners or syndicate members, subject to limits on the portion allotted to qualified institutional buyers. The issuer enters an underwriting agreement with the book runner, who agrees with syndicate members on specified securities and predetermined price for under-subscription. Lead book runners must cover syndicate defaults and satisfy minimum underwriting obligations; underwriting may only be used to fulfil obligations and, if the entire offer is underwritten, obligations cover the whole offer.