Blockchain can help IoT and smart city and community related services and applications to establish trust, accountability and transparency while streamlining business processes. In order to promote the integration of blockchain with the IoT infrastructure, as well as enable richer flexible service scenarios for different IoT and smart cities and community verticals, this Recommendation, from the IoT point of view, identifies the functionalities of the blockchain, specifies the requirements of blockchain enabled IoT, and describes the specific IoT capabilities that are necessary to support blockchain.