An anonymous trading system for financial instruments comprises a network of broking nodes each performing a bid and offer matching function and a market view distribution function. Trader terminals are connected to the network via trading agent nodes. During deal execution a credit check is performed and once the deal is complete the identity of the counterparty becomes known to the other counterparty to the deal. The originating counterparty may send a More quantity message to the other party proposing a further deal at the same price. The other party may decline, partially accept, accept or accept and propose a still further amount. Credit for the further deal is drawn from an external source and the internal credit limits are temporarily increased or disabled to prevent the deal from being rejected.