Home Postcode finder QLD Plainby Plainby postcode QLD Plainby is a locality in Queensland covered by postcode 4355. Postcode 4355 State or territory Queensland (QLD) Region Toowoomba Region Add a free Plainby business listing Be the first listing in Plainby Common questionsWhat is the postcode for Plainby?Plainby, QLD has the postcode 4355.What state is Plainby in?Plainby is in Queensland (QLD).Does postcode 4355 cover more than one suburb?Yes. Postcode 4355 covers 12 localities, so the postcode alone does not identify Plainby. Browse other postcodes in Queensland, or widen the search to every Australian postcode.