IWL's most important customer is Westpac and the bank is free to walk away from IWL and CBA from September 2009 under the terms of a contract renewed in 2004.Westpac first sourced broking services from JDV - then an independent company - in 2001.Under the Westpac services agreement, JDV provides the technology and transaction processing for Westpac's stockbroking arm.Westpac accounted for 40 per cent of IWL's wholesale broking business - measured by contract notes executed - in the year to June 2007.BT Wrap's contract for the provision of portfolio administration services by IWL to BT also expires in September 2009.In the year to June 2007 more than 50 per cent of the EBITDA profit of IWL's wholesale broking business was generated under contracts with Westpac and National Australia Bank (see next article).Westpac may find it relatively easy to establish alternative arrangements if - as rumoured, and contrary to the assumption of Lonergan Edwards - it were to make plans to move its business away from IWL.The scheme booklet noted that JDV provides the front and back office functions only, with Westpac using its own ASX participant ID. Under this arrangement Westpac retains all obligations and risks for regulatory, settlement and compliance matters.