Stamp duty is a tax imposed by all Australian states and territories on certain instruments and transactions. As each jurisdiction has its own stamp duty laws, the instruments and transactions that are dutiable, the applicable rates of duty, the person(s) liable to pay duty and the time for payment of duty vary among the jurisdictions.

Generally, an instrument or transaction may be dutiable in a particular jurisdiction where it affects property in the jurisdiction or the instrument is executed by a party in the jurisdiction.

Depending on the jurisdiction and type of instrument or transaction, the applicable duty payable may be “nominal” (ie a fixed amount, generally because a concession applies) or “ad valorem” (ie imposed on a sliding scale, with higher rates of duty being payable as the value of the transaction increases).

The sanctions for the non-payment of duty are broadly similar across the jurisdictions, with penalty tax and interest applying to unpaid duty, and unstamped instruments being unenforceable and inadmissible in evidence until the correct duty is paid.

The stamp duty laws in most Australian jurisdictions prescribe certain transactions as “dutiable transactions”. The types of transactions that are dutiable vary between the jurisdictions, although most jurisdictions prescribe agreements for sale or transfer, transfers and declarations of trust over “dutiable property” (such as land) as “dutiable transactions”. A liability for duty may arise regardless of whether the transaction is documented. South Australia has a broader base and imposes duty on a wider range of instruments and transactions within the extended definition of “conveyance”.

In the Australian Capital Territory, dutiable transactions attract ad valorem transfer rates of duty of up to 6.75% of the greater of the consideration or unencumbered value (ie without reference to encumbrances, such as mortgages) of the “dutiable property”. In most jurisdictions, the purchaser or transferee is the party liable to pay the duty.

The stamping arrangements for “dutiable transactions” vary between the jurisdictions, with time for lodgment and/or payment of duty generally being different in each jurisdiction. See Dutiable transactions.

On 1 July 2016, New South Wales became the last jurisdiction to abolish mortgage duty.

Previously, mortgage duty applied to instruments within the prescribed meaning of "mortgage" (such as mortgages and charges) over property in the relevant jurisdiction.

Duty was generally payable at the rate of 0.4% of the amount of "advances" (for example, loan funds actually advanced) secured by the mortgage multiplied by the percentage of the value of the property secured in a particular jurisdiction as compared to all property secured. The mortgagor was generally the party liable to pay the duty.

A mortgage that was liable to duty is unenforceable to the extent of any amount secured by the mortgage on which duty has not been paid. See Mortgage duty.

Concessional (ie nominal) stamping is available among the various jurisdictions for certain dutiable transactions and conveyances that would otherwise attract ad valorem duty. However, there is no concept of stamp duty concessions in Victoria.

Common examples include transfers of dutiable property on a change of trustee, transfers between apparent and real purchasers of dutiable property and transfers of dutiable property arising in respect of deceased estates.

Most jurisdictions have prescribed forms which need to be completed and documentary evidence which needs to be provided to obtain the benefit of these concessions. See Duty concessions.

A number of exemptions from stamp duty are available among the jurisdictions for dutiable transactions and conveyances that would otherwise attract ad valorem duty.

Common examples include first home purchases, transfers of dutiable property on a relationship breakdown or between related corporations.

Most jurisdictions have prescribed forms which need to be completed and documentary evidence which needs to be provided to obtain the benefit of these concessions. See Exemptions from duty.