The banking system in New Zealand is a relatively simple one structurally and comprises a central bank–the Reserve Bank of New Zealand–five commercial or trading banks (each with its own private savings bank), trustee savings banks, and the New Zealand Post Office Savings Bank. A number of other institutions in New Zealand notably the stock and station agency companies also undertake some functions usually regarded as distinctive to banking business. But as such transactions as the acceptance of deposits and the operation of current accounts that may be drawn on by cheque or order are normally a relatively small proportion of their total business, and as their total deposits are small compared with those of the trading banks, they are not required to comply with legislation relating to banks. This position, however, may change in the future.

In the banking system the central bank is the youngest member apart from some of the trustee savings banks and the private savings banks which opened in October 1964. This position is by no means peculiar to New Zealand and reflects the tremendous changes in banking and in attitudes towards monetary or credit policies since the early nineteen thirties. The Reserve Bank of New Zealand commenced business in 1934, almost 100 years after the first trading bank began business in this country. The Union Bank of Australia later merged in 1951 with the Bank of Australasia into the Australia and New Zealand Bank Ltd., opened in New Zealand in 1840. Of the other four trading banks two, the Bank of New South Wales and the Bank of New Zealand, commenced business in 1861 and have thus recently celebrated their centenaries. The National Bank of New Zealand Ltd. began business in 1873, while the latest and most recent was the Commercial Bank of Australia which commenced business in this country in 1912.

The trustee savings banks have an equally long history, the first such being established in Auckland in 1847. By 1870 nine trustee banks were in existence but four, Lyttelton, Wellington, Napier, and Nelson, did not survive the turn of the century. The five remaining ones–Auckland (1847), New Plymouth (1850), Dunedin (1864), Invercargill (1864), and Hokitika (1866)–have prospered.

The Trustee Savings Banks Amendment Act of 1957 gave authority to the Minister of Finance to approve in certain circumstances the opening of new savings banks, and in June 1959 the Waikato Savings Bank began business in Hamilton. Since then several other banks have been established.

The Post Office Savings Bank, by far the biggest savings bank, was established in 1867, and has since grown into a major financial institution .