When you're thinking about where to keep your hard-earned money in Australia, it's hard to ignore the giants. We're talking about the 'Big Four' – Commonwealth Bank of Australia (CBA), Westpac, National Australia Bank (NAB), and Australia and New Zealand Banking Group (ANZ). These four institutions collectively hold a staggering 70% of the Australian financial market, managing assets that dwarf most other players in the sector. As of early 2025, their combined assets were well over $3.8 trillion, a significant chunk of the nation's nearly $5.5 trillion banking sector.
It's interesting to see how they stack up against each other. CBA consistently leads the pack, not just in total assets but also in market capitalisation. It's a bit of a historical anomaly, being the youngest of the four, established in 1911 and privatised in 1996, yet it once served as the central bank before the RBA took over that role in 1960. Westpac often sits in the second spot, a position it solidified through strategic mergers, notably with St.George Bank in 2008, and acquisitions like BankSA and RAMS. NAB, formed from the union of two century-old banks, usually follows, with its assets including those from subsidiaries like UBank and Bank of New Zealand. ANZ, while currently the smallest of the group, is poised for growth with its significant acquisition of Suncorp Bank, which will push its assets past the $800 billion mark.
Beyond sheer size, what really sets these banks apart is the 'Four Pillars Policy'. This isn't just a friendly agreement; it's a law that essentially prevents these four from ever merging with each other. It's a key piece of legislation designed to maintain a certain level of competition, even as these majors have been busy expanding their reach by acquiring smaller banks over the years.
When it comes to where Australians are placing their trust for savings, the Big Four are again the clear frontrunners. Their combined household deposits represent over 70% of all cash deposits held by authorised deposit-taking institutions in the country. CBA leads in this area too, followed by Westpac, NAB, and then ANZ. This widespread trust is understandable, given their long history and extensive branch networks.
However, just because they're the biggest and most popular doesn't automatically mean they're the best fit for everyone's savings goals. While their savings accounts often offer similar interest rates and features, the real differentiator often comes down to how well a specific product aligns with your personal savings strategy. Comparing the base variable rates is a good starting point, and don't forget to look into any introductory bonus rates that might give your savings an initial boost. Ultimately, while the Big Four offer a solid foundation for banking, a little digging into their specific offerings can help you find the one that truly works for you.
