Analysts flag 'improbable' mortgage data

UBS analysts say home loan borrowers could be lying about how much they earn, but they aren't sure to whom.

Home loan borrowers could be lying about how much they earn but analysts aren't sure whether they are fibbing to their banks, the ATO, the census or the Australian Bureau of Statistics.

UBS analysts Jonathan Mott and Rachel Bentvelzen are warning that income levels reported to banks are "highly improbable" compared to various official figures, which suggests borrowers could be overstating their income to lenders and exposing them to material risk.

But the analysts say Commonwealth Bank, National Australia Bank and Westpac data implying 42 per cent of home loans last year went to people with gross incomes of more than $500,000 could also mean people are understating their income to the Australian Taxation Office.