The 10-year agreement involves the transfer of 1,300 employees to EDS. Sources close to the deal said the contract would be signed on 27 September after months of negotiations.
In May this year, Westpac invited EDS and Unisys to bid for the lucrative tender which covers the processing and servicing of mortgages.
Key to the bidding criteria was the ability to show potential to "significantly upgrade" technology, move to straight-through processing, enhance customer service and reduce costs.
The bank wants access to a worldwide infrastructure in order to exploit the rapidly changing technology environment.