Taken from the Sapol web site:
What crashes need to be reported?
A crash is required to be reported to a police officer by a driver involved in a crash if real or personal property (other than an animal) is destroyed or damaged,
except where:
(a) the only property destroyed or damaged is property owned by the driver; or
(b) a fair estimate of the cost of making good the damage to property is not more than $1,000.