Online bank ING Direct has completed a major technical and design overhaul of its banking platform which the bank's executive director customer delivery Lisa Claes said was the largest single investment the "digital first" bank had ever made.While declining to give a precise figure, Claes said the upgrade had cost "tens of millions of dollars" over the past 18 months.ING Direct has succeeded in standardising all 18 systems it was running into one system so any new products added will instantly adapt to all the rest of the system.The rebuild is part of a multi-year plan to create a more complete retail banking product suite, and to make more customers aware of what's on offer. It also means that once a customer is signed up for one product all the information given can be captured as a core of generic material and "migrated" into any other later product application that a customer might make."In an era where digital is becoming the preferred channel for many people to do their banking - and for ING direct, the only channel - a key challenge for us is becoming our customers' primary bank," said Claes."Many of our customers, with minimal change to their behaviour, can make us their primary bank, with the benefits that brings. They just don't know what they can do to achieve this.""So [this project] is more about deepening the relationship with existing customers - and we hope we will attract new customers - but that's not our main angle."It will also allow ING's interactions with customers to be based on their current product holdings and the preferences they have displayed - not on what the bank thinks they need."This is the blueprint for the way the bank will operate in the future," said Claes.Claes said the platform rebuild, which she compared to a major house renovation rather than a rip down and rebuild operation, was managed in stages through an iterative process of testing that started with "a couple of thousand customer volunteers" but grew by stages until, by pre-launch last week, there were 16,000 "pilot customers".This allowed ING Direct's technology team to iron out the bugs as the upgrade progressed. The new website also has a feedback feature allowing the bank to make continuous improvements quickly, Claes said.Down the track ING Direct may well introduce more sophisticated offerings, such as a wealth management suite of products and services, but is not high on the list at present, said Claes. "If you look at what the primary bank customer requires, certainly it is not in the higher-order needs but wealth management is in the hierarchy," she said."We will continue to explore opportunities there but that's not on our roadmap this year but, given it is in primary bank customer territory, that we've got super [products] - which is a large part of most Australians wealth management strategy - and that we have over $2 billion in funds under management and 50,000 customers we will be looking at if and