Customer retention is what is thought to be behind BNZ's decision to take on KiwiSaver.
The bank has announced it'll offer its customers KiwiSaver plans - the last of the big banks to do so.
Massey University senior lecturer in banking, Claire Matthews, says BNZ needs to offer the same as its competitors so customers don't jump ship.
"Certainly it'll be about making sure they can provide a full range of banking services, because it will make it easier for them to attract customers."
She says it's been a long time coming for BNZ.
"There's a recognition that a lot of members like to have their KiwiSaver accounts with their banks, and therefore if the BNZ is not offering KiwiSaver and members want to do that, then they may be choosing to take their bank accounts elsewhere."
Claire Matthews says the bank might not have been convinced about the benefits of being involved with KiwiSaver, but now it's recognised it's a long term scheme it needs to be part of.