In its official document to Abbey National's shareholders, Spain's biggest bank said that using its core banking system, Partenon, to run Abbey's IT would save £305m from 2007.
Partenon is an in-house IT platform that has been developed by Santander to rationalise and cut costs following a spate of acquisitions by the bank in Spain.
Abbey National currently runs multiple legacy platforms that it gained when it bought insurance companies Scottish Mutual and Scottish Provident.
Santander has said it would cut 3,000 of Abbey's workforce over three years if the deal goes through but neither it nor Abbey would comment on whether IT staff would be affected.
As well as introducing IT management practices that it already uses in Spain, Santander is proposing to cut investment in existing IT projects and processes that fail to match its Partenon strategy. Projects that would be either difficult or impossible to move on to the Partenon platform would be the most likely to face the axe.
Abbey's main IT proposition is an online platform that can aggregate all the individual investments held by any customer of its subsidiary businesses.
Santander also expects to generate further IT savings by negotiating better terms with suppliers because the takeover would make the group one of the biggest banks in the world. Savings would also come from speeding up Abbey's existing plan to outsource its back office in the UK and reduce the size of the remaining sites.
From 2007, Santander will migrate Abbey's IT to Partenon, system by system. Santander believes that introducing a single customer database and electronic products will lead to more cross-selling of products.