Reliance Industries has overtaken state-owned Oil and Natural Gas Corp to become the nation's most profitable company, posting a consolidated net profit of Rs 23,566 crore in the 2014-15 fiscal. ONGC, which posted a consolidated net profit of Rs 18,334 crore in 2014-15, slipped to number three, behind RIL and Tata Consultancy Services Ltd, India's largest IT firm, according to earning data of listed firms available on the BSE.