Home Postcodes by state WA 6003 Postcode 6003 6003 is the postcode for 2 localities in WA: Highgate and Northbridge. Localities with postcode 6003HighgateWANorthbridgeWA Postcode 6003 State or territory Western Australia (WA) Localities 2 Council area Vincent; Perth Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6000 · Postcode 6004