This Practice Note explains the how communications data can be lawfully obtained and disclosed by public authorities under the Investigatory Powers Act 2016 (IPA 2016). It explains the lawful interception of communications, the types of interception warrants which can be obtained, including targeted interception warrants, targeted examination warrants and mutual assistance warrants, applications for warrants and information which are excluded from warrants. The safeguards in place for obtaining communications data, specifically in relation to legally privileged material and journalist material are explained as well as the offences of unauthorised disclosure, and knowingly fail to comply with the obligation to give effect to an interception warrant.