Australians will find it harder to take out new home loans with the Commonwealth Bank after the lender tightened repayment tests for borrowers.

When customers with an existing CBA home loan apply for a new home loan, the bank will assess their ability to continue to repay the existing home loan in the same way they assess their ability to pay a new home loan.

That is, the bank will apply an interest rate buffer of either 7.25% or the current product interest rate plus 2.25%, whichever is higher.

Customers with an existing home loan with another lender who apply for a Commonwealth Bank loan must demonstrate they can afford repayments on their existing loan plus 30%.