There are 2 types of assurance of support. Which one you need depends on the visa type.
To get some types of visas you must have an assurance of support. These are:
- aged dependent relative
- contributory parent, contributory aged parent, parent or aged parent
- remaining relative
The assurer must give a bank guarantee.
Some visas may need an assurance of support. It's up to the Department of Immigration and Border Protection to decide in each case. These visa types are:
- former resident
- orphaned relative under 18
There's no need for a bank guarantee, unless the assurer is an incorporated or unincorporated organisation.