1. A system for terminating outstanding derivative transactions between a plurality of parties, each transaction being described by a transaction record provided by one of the parties to the transaction, the transaction record including trade details identifying the transaction, the trade details at least specifying two parties to the transaction, the transaction record providing one party's valuation of the net present value of the transaction, and at least one risk characteristic of the transaction, the system comprising: a plurality of data input/output and processing stations for transmitting a transaction record from each party; a central processing station; and a communications network operatively interconnecting all of the stations; wherein the central processing station comprises: linking means for linking together two transaction records from two different parties relating to the same transaction, the linking means being arranged to use a plurality of items of the transaction record to determine records from different parties corresponding to the same transaction; and combining means for combining together a plurality of linked transaction records to determine a termination proposal for terminating a plurality of the transaction records prior to their maturity dates, the central processing station being arranged to transmit the termination proposal to the data input/output and processing stations of the parties involved in the proposal.