Home Postcode finder WA Lake Austin Lake Austin postcode WA Lake Austin is a locality in Western Australia covered by postcode 6640. Postcode 6640 State or territory Western Australia (WA) Region North West Suburbs Add a free Lake Austin business listing Be the first listing in Lake Austin Common questionsWhat is the postcode for Lake Austin?Lake Austin, WA has the postcode 6640.What state is Lake Austin in?Lake Austin is in Western Australia (WA).Does postcode 6640 cover more than one suburb?Yes. Postcode 6640 covers 5 localities, so the postcode alone does not identify Lake Austin. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.