The average Australian homeowner is paying around $1,200 a month on a mortgage that they never borrowed, according to a survey by Credit Suisse.
It was also the top-ranked debt-servicing cost among those who have borrowed, the bank found.
The most-borrowed loan, on average, was $1.4 million, with an average monthly payment of $1 million.
Credit Suisse found that Australians have the highest interest rates of all borrowers with loans, at 2.9 per cent, followed by Australians with student loans (2.6 per cent) and those with a business loan (2 per cent).
For the most part, the highest average interest rate was in Sydney ($1,250), followed by Perth ($1.9), Melbourne ($1) and Adelaide ($1).
Australia’s most indebted borrowers are in Sydney, with a median debt of $5,000.
For a second consecutive year, the most-debt-serviced mortgage was a one-year fixed-rate, with the average payment of just $600 a month.
In Melbourne, where the median debt was $4,000, the median monthly payment was $900.
Australia was the second most indebted country for the third year in a row, behind the United States, with debt levels of $21,800 for the year, up from $17,400 a year ago.
A second Credit Suise report found Australians were not the most likely to have a mortgage they paid back, with only 1 in 10 of those who had a loan repaid a loan.
More: The latest mortgage data and analysis for September.