Banks to reveal how Iran conflict has affected earnings

As Australian home owners stare down the barrel of more interest pain and higher inflation due to the Middle East conflict, the major banks are laying down defences.

ANZ, National Australia Bank and Westpac are due to report their interim results from Friday, and while the news is likely to be solid, less-sunny days could lie ahead.

This set of banking earnings covers the six months ended March 31, a period that includes the US-Israeli war on Iran that began in February and has sparked a huge jump in energy costs.

The banks have since had to deal with Donald Trump-driven market volatility and set barriers for a potential uptick in bad debts held by customers struggling with rising living costs and impending increases in lending rates.

NAB has already warned its first-half results will include $706 million in credit impairment charges, while Westpac has warned that geopolitical uncertainty and the associated increase in market volatility have affected its earnings.

Fidelity International's Australian analyst and portfolio manager, Zara Lyons, told AAP this set of results would likely be strong in terms of business credit and mortgage growth.

"It's a bit of a mixed bag, but I would have said, had we not had the energy situation, that the banks had been in very good health coming into this period," she said.

"The outlook is looking a little less shiny than it did.

"But I still think that they are very resilient and should be able to navigate this world."

Josh Gilbert, lead Australia-Pacific market analyst for eToro, said the Reserve Bank's back-to-back rate hikes in 2026 were, on paper, a tailwind for bank margins.

"But higher rates are a double-edged sword - they lift margins on one side of the ledger while squeezing the borrowers on the other, and that is where the pressure starts to build on provisioning and credit quality," he said.

Bank watchers will be looking at how far they lean into provisioning - the size of the buffers they put aside for losses they have not yet seen.

"If the banks are leaning in hard, that is management signalling what they're seeing in the household and business book," Mr Gilbert said.

They would also look at net interest margins, a key measure of profitability, and capital returns, Mr Gilbert said.

Westpac, he noted, was sitting on surplus capital and had the biggest pile of franking credits in the sector, which put a special dividend firmly on the table.

"The results, as ever, will be important, but what management says about the road ahead will likely matter more," he added.

"The market is clearly bracing for cautious tones across the sector."

ANZ will lead off with its results on Friday after making a $1.94 billion cash profit in the first quarter, followed by NAB ($2.02 billion) on May 4, and Westpac ($1.9 billion) on May 5.

Commonwealth Bank will issue its third-quarter update on May 13.