Australia
Australia Postcode Format Explained
Australian postcodes are four digits long. See what the first digit signals, how a valid postcode looks and the mistakes that cause failed forms.
Updated 14 October 2026 · 3 min read
An Australian postcode is a four-digit number issued by Australia Post. It identifies a delivery area and is written at the end of the address, after the suburb and the state or territory. The format is simple, but a few details cause problems in online forms and databases.
The four-digit structure
The code has no letters, spaces or hyphens. Its first digit broadly indicates the state or territory:
- 0: Northern Territory
- 1: large-volume mail receivers, mostly in New South Wales
- 2: New South Wales and the Australian Capital Territory (the ACT also has codes beginning with 02)
- 3: Victoria
- 4: Queensland
- 5: South Australia
- 6: Western Australia
- 7: Tasmania
- 8: Victoria, mainly for post office boxes and large-volume mail users
- 9: Queensland, mainly for post office boxes and large-volume mail users
The remaining digits narrow the code to a region, and then to a specific delivery area or post office. The digits after the first do not follow a rule that ordinary users need to memorise, so the practical approach is to look up the postcode rather than guess it.
Not every range maps neatly
The ranges above are a general pattern, not a strict border. Australian Capital Territory addresses use codes that begin with 2 or 0, and some border towns have postcodes belonging to the neighbouring state. Several external territories, such as Christmas Island and the Cocos (Keeling) Islands, have postcodes that begin with 6. Treat the first digit as a hint, not as proof.
Examples of valid format
These values only illustrate the shape of the code. They are generic, and a real address needs a real lookup:
- 2000
- 3000
- 4000
- 0800
Anything shaped like four digits is syntactically valid, whether or not it is assigned to a delivery area.
Postcodes are not unique to a suburb
One postcode can cover several suburbs, and one suburb can sometimes have more than one postcode. That is why systems that ask for a postcode should also keep the suburb and state. A postcode alone is not enough to place a house on a street, and it does not describe an exact point. For precise positioning, a location code such as a UPCS code (prefix AU) can be added next to the address; see how to write an Australian address.
Common mistakes
- Dropping the leading zero when a code like 0800 is saved as a number.
- Entering a five-digit value copied from another country's format.
- Writing the postcode before the state instead of after it.
- Using a postcode that belongs to a PO Box range for a physical street address, or the reverse.
- Assuming the postcode matches the suburb name without checking it.
If you are unsure, follow the steps in how to find an Australian postcode. For an overview of the whole system, return to the Australia guide.
Frequently asked questions
How many digits does an Australian postcode have?
Four. Australian postcodes are always four digits, and a code with fewer or more digits is not valid.
Can a postcode start with zero?
Yes. Some postcodes, for example in the Northern Territory and parts of the Australian Capital Territory, begin with 0. The leading zero must be kept, so store postcodes as text rather than numbers.