The combined profits of Australia's big four banks likely exceeded $15 billion in the first half, as lenders started to benefit from a round of late 2016 interest rate hikes and strong home loan growth.

Big four investors have enjoyed share price gains of more than 6 per cent so far this year, and half-year results from three of the big four in the coming weeks are expected to show profits also ground higher across the industry.

Even so, there remains a question mark about whether National Australia Bank and Westpac can sustain their dividends, as the industry prepares for looming rules that may force lenders to set aside billions more in capital.

ANZ Bank will kick off the half-year bank reporting season this Tuesday, with analysts tipping a $3.5 billion cash profit in the six months to March, and a flat interim dividend of 80¢ a share.