Damage caused when a tenant makes changes to the house or flat
In some situations tenants can ask to make changes to the property, such as renovations and attaching fixtures (eg, brackets for shelving).
If the attachment of the fixture is a "minor change", tenants must remove it and change things back to "substantially" how they were at the beginning of the tenancy, unless they have agreed with the landlord that the fixture can stay (s 42B(4)-(6) RTA).
If a tenant has attached a fixture, the tenant may remove it when they leave, unless that would cause irreparable damage (s 42(3) RTA). If they do cause damage when they try and remove it, the tenant must inform the landlord immediately. The landlord can choose whether the tenant must either repair the damage or compensate the landlord for any reasonable expenses incurred in doing the repairs (s 42(6) RTA).
Unless the damage was intentional or caused by an action that is an imprisonable offence, then the tenant’s liability will be limited to the "cost limit" associated with carelessness (s 49B(6) RTA).
Damage caused by someone other than the landlord or tenant
If a guest of the tenant damages the property, the landlord is allowed to treat the issue as if it was the tenant that caused the damage (s 41(1) RTA).
Anyone who is on the property with the tenant’s permission (except for the landlord or the landlord’s contractors / agents) will be assumed to be a guest of the tenant (even if the tenant isn’t there at the time), unless the tenant proves that they took reasonable steps to prevent them from coming on to the property, or tried to make them leave (s 41(2) RTA).
If someone who is not the tenant’s guest damages the property (such as a burglar or the landlord’s contractor), the landlord is responsible for the problem.
If the tenant has a party that gets out of control and property is intentionally damaged, the landlord is allowed to presume that all the people were guests of the tenant (meaning the tenant will be held responsible).
To avoid being responsible for the damage, the tenant would need evidence to show that they took reasonable steps to stop the people from coming onto the property, or tried to get them to leave (eg, calling the police).
'Acts of God' (eg, storms)
'Acts of God' are natural events like storms and earthquakes. The landlord is responsible for fixing damage caused by acts of God.