Home Postcode finder SA Southend Southend postcode SA Southend is a locality in South Australia covered by postcode 5280. Postcode 5280 State or territory South Australia (SA) Region SA Outer Suburbs Add a free Southend business listing Be the first listing in Southend Common questionsWhat is the postcode for Southend?Southend, SA has the postcode 5280.What state is Southend in?Southend is in South Australia (SA).Does postcode 5280 cover more than one suburb?Yes. Postcode 5280 covers 16 localities, so the postcode alone does not identify Southend. Browse other postcodes in South Australia, or widen the search to every Australian postcode.