Fair market value of employee share options determines fringe benefit tax liability on vesting under prescribed valuation rules. Rule 40C prescribes that fair market value of an equity share for fringe benefit tax is determined on the option vesting date: for listed shares it is the average of opening and closing prices on that date (using the exchange with highest trading volume where multiple listings exist, or the nearest preceding closing price if no trading occurs); for unlisted shares it is the value determined by a category I merchant banker on the specified date. Definitions specify opening/closing price, merchant banker, recognised stock exchange, specified date and equity share.