As a clearinghouse and Central Counterparty, SIX x-clear occupies an intermediary position between the trading parties.
As a Central Counterparty, SIX x-clear
Clearing is effected after a trade has been executed (matching) and before it is settled. The purpose of clearing is the efficient handling of risks inherent in executed but still unsettled (trading) contracts. The Central Counterparty steps into the contracts as intermediary and represents the buyer to each seller and the seller to each buyer.
A list of clearing-eligible securities will be made available for each of the exchanges.
Further information is available on the website of SIX SIS.