Home Postcodes by state NSW 2303 Postcode 2303 2303 is the postcode for 3 localities in NSW: Hamilton, Hamilton East and Hamilton South. Localities with postcode 2303HamiltonNSWHamilton EastNSWHamilton SouthNSW Postcode 2303 State or territory New South Wales (NSW) Localities 3 Council area Newcastle Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 2302 · Postcode 2304