This chapter focuses on licences implied by custom. A custom in this context represents the conduct of a community (of members of a trade, profession, industry, or market), as opposed to an individual copyright owner enabling the copyright work to be used in a particular way. So long as the community within which the custom is alleged represents the copyright owner, the community’s conduct will be taken as being on behalf of the copyright owner. Once established, a custom does not require validation by a court of law for it to be binding, so that a custom becomes an independent source of power that drives the implication of a copyright licence. Also, once established, a custom can be the basis for implying both a bare licence and a contractual licence, depending on the content of the custom. Therefore, the chapter analyses the case law within a single framework for implying both bare and contractual licences. It builds on the criteria developed by the courts in commercial law to establish a custom (certainty, notoriety, and reasonableness), incorporating factors specific to the copyright context.