Home Postcodes by state WA 6421 Postcode 6421 6421 is the postcode for 3 localities in WA: Burracoppin, South Burracoppin and Warralakin. Localities with postcode 6421BurracoppinWASouth BurracoppinWAWarralakinWA Postcode 6421 State or territory Western Australia (WA) Localities 3 Council area Merredin; Westonia Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6420 · Postcode 6422