APRA required serviceability assessments for new loans to be more conservative by basing them on the required principal and interest payments over the term of the loan remaining after the interest-only period. (Previously, some banks were assuming that the principal was being repaid over the entire life of the loan, which was clearly a lower bar for the borrower to meet.)
At about the same time, APRA acted to ensure that the interest rate ‘buffer’ used in the serviceability assessments for all loans was at least 2 percentage points above the relevant benchmark rate (with an interest rate floor of at least 7 per cent). Also, that test was required to include other, existing debt (which is often substantial for investors).