Some overseas banks are also taking a tough stance on what constitutes a second home.

The most common way of defining second-home is to see the mortgage record - if a home owner has bought two homes but has only one mortgage, a further mortgage application is deemed as a second-home mortgage.

In beefing up curbs on home credit, some banks follow the bigger number principal - no matter whether it's mortgage credit or home ownership, the bigger number will apply to decide new mortgage applicants.

For example, if someone has two homes, one of which is mortgaged, the new mortgage application is deemed as a third as two homes are already owned. Currently it would be defined as a second mortgage.

There's market speculation that the regulator may set the bar on home numbers rather than mortgage numbers.