Treatment adherence status of the TB patients notified from private sector and its associated factors: Findings of a secondary data analysis from West Bengal, India

•This is one of the few studies which described the treatment adherence status among private TB patients.•Private TB patients are highly vulnerable to non-adherence and once defaulted, it is difficult to retrieve. (retrieval rate is 36.9%).•Commonest Reasons stated for being a defaulter were ‘Medicine is not working’ (30%), ‘Travel’ (28.6%) and ‘Cost involved in the treatment’ (21.8%).•Higher default rate was associated with 15–59 years age, males, addiction, DR-TB, continuation phase of treatment, and previous history of TB.•Now as India is moving towards TB elimination, strict treatment adherence mechanism, especially for private TB patients is a need of hour.