The Mindfulness-Based Interventions: Teaching Assessment Criteria (MBI:TAC) is a measure of teacher competency and intervention fidelity in the delivery of mindfulness-based programs (MBPs). The tool has six domains that intersect with six stages of competence development. The domains offer a map of the landscape of skillful mindfulness teaching and a shared language, informing the structure and content of teacher training pathways, supervisory frameworks, and reflective practice. The MBI:TAC has good inter-rater reliability when administered by trained experts. It is a process driven tool that sensitively preserves the underpinning ethos of the mindfulness-based approach while enabling relative objectivity in the assessment process. Certification of competency through the MBI:TAC represents the highest qualification available for trained mindfulness teachers, supporting parity in standards of recognition.