An undercover officer, such as might be used by the police to detect serious organised crime, or by a council’s trading standards team to detect serious fraud, are authorised in exactly the same way as any other CHIS. Whilst different terminology might be used (a test purchase officer, a Covert Internet Investigator, etc), their lawful authorisation is determined by RIPA/RIP(S)A, just the same as would be a member of the public authorised to report on criminality amongst those they know.