The Credit Rating and Information Services of India (Crisil) has assigned a triple-A rating to Tata Sons Rs 75 crore debenture issue. "The ratings continue to reflect Tata Sons leading business position in the Indian software industry through its division, Tata Consultancy Services as well as its significant financial flexibility arising from its status as the principal-holding company of the large and diversified Tata Group", Crisil said.