Home Postcode finder NSW Underbank Underbank postcode NSW Underbank is a locality in New South Wales covered by postcode 2420. Postcode 2420 State or territory New South Wales (NSW) Region Hunter Add a free Underbank business listing Be the first listing in Underbank Common questionsWhat is the postcode for Underbank?Underbank, NSW has the postcode 2420.What state is Underbank in?Underbank is in New South Wales (NSW).Does postcode 2420 cover more than one suburb?Yes. Postcode 2420 covers 23 localities, so the postcode alone does not identify Underbank. Browse other postcodes in New South Wales, or widen the search to every Australian postcode.