New Delhi, Sept. 12 -- In a David-versus-Goliath battle, India's smaller audit firms are sharpening their game. As more than 600 large companies prepare to change auditors over the next two years, these audit firms, with teams of just a few hundred, are investing in technology, building specialist teams and competing hard on fees to wrest bigger, more valuable clients away from the Big Six in the country's largest-ever audit rotation exercise underway.

Their trump card is a smaller but more consistent team, one that is not typically vulnerable to partner poaching, and where there is no cross-selling of other services alongside audit.

Deloitte Haskins & Sells, S.R. Batliboi & Co. (the audit network firm for EY Global), Price Waterhouse L...