RBI guidelines for charges on non-maintenance of minimum balance:
1) Banks should notify the customer clearly by SMS/ email/ letter etc. that in the event of the minimum balance not being restored in the account within a month from the date of notice, penal charges will be applicable.
2) Penal charges should be reasonable and not out of line with the average cost of providing the services.
3) Balance in the savings account should not turn into negative balance solely on account of levy of charges for non-maintenance of minimum balance.
Source- Notification dated 20th Nov'14 issued by Apex Bank