national australia bank (abbreviated nab, branded nab) is one of the four largest financial institutions in australia in terms of market capitalisation, earnings and customers. nab was ranked 21st largest bank in the world measured by market capitalisation and 52nd largest bank in the world as measured by total assets in 2019. nab operated 1,590 branches and service centres; and 4,412 atms across australia, new zealand and asia serving 12.7 million customers.