What negative gearing actually is
Negative gearing is a description, not a plan. A rental property is negatively geared when the deductible costs of holding it exceed the rent it earns for the year. Those costs typically include the interest on the loan used to buy it, council and water rates, land tax, strata or body corporate fees, landlord insurance, property-management fees, repairs and maintenance, and depreciation. When the total of those exceeds the rental income, the property runs at a net rental loss for the year.
Under current Australian rules, that net rental loss can generally be offset against your other assessable income — most commonly salary or business income — which lowers your taxable income for the year. That offset is the whole of what “negative gearing” refers to. It is not a special scheme you opt into; it is simply the ordinary deductibility of expenses incurred in earning assessable income, applied to a property that happens to cost more to hold than it earns.