Behavioral Health Coverage Transparency Act of 2018 This bill amends the Public Health Service Act, the Employee Retirement Income Security Act (ERISA), and the Internal Revenue Code to require the Departments of Health and Human Services (HHS), Labor, and the Treasury to: (1) cooperatively issue regulations to require group health plans and health insurance issuers to annually disclose the analyses performed to ensure compliance with mental health parity laws, and (2) conduct annual random audits of group health plans and health insurance issuers to determine compliance. HHS must establish a consumer parity unit: (1) to facilitate the collection of, monitoring of, and response to consumer complaints; and (2) to provide consumers information about the disclosure requirements and enforcement of the mental health parity laws.