One of three common structural approaches, or models, for linking delivery and payment in a securities settlement system (identified by the Committee on Payment and Settlement Systems of the Bank for International Settlements). Model 1 denotes Gross, Simultaneous Settlements of Securities and Funds Transfers. These systems settle transfer instructions for both securities and funds simultaneously on a trade-by-trade (gross) basis, with final (irrevocable and unconditional) transfer of securities from the seller to the buyer (delivery) occurring at the same time as final transfer of funds from the buyer to the seller (payment). The securities settlement system maintains securities accounts and funds accounts for participants. Transfers of securities and cash are made by book-entry.