Closing Price (Weighted Average)
The official closing price of an equity security on NSE is calculated as the volume-weighted average price (VWAP) of all trades executed during the last 30 minutes of the regular trading session (3:00 PM to 3:30 PM), rather than the price of the last trade at 3:30 PM.
The methodology for computing the official closing price on Indian equity exchanges evolved to address a persistent market integrity concern: the possibility of price manipulation through concentrated trading in the final seconds of the trading day, which was a known tactic in some global markets before exchanges adopted more robust closing price methodologies.
NSE introduced the 30-minute VWAP-based closing price computation as a more representative and harder-to-manipulate measure. The VWAP gives greater weight to trades executed in larger volumes, meaning a handful of small trades at an outlier price near the session end have minimal impact on the closing price. If no trades occur during the 3:00 PM to 3:30 PM window (possible for illiquid securities), the last traded price for the day is used as the closing price.
The closing price carries significant downstream consequences. Mutual funds use it to compute their Net Asset Values (NAVs), which are typically published after the close using this official price. Margin obligations for derivative positions are recalculated based on the closing price of the underlying. Circuit-breaker limits for the next trading session—upper circuit and lower circuit levels—are expressed as a percentage of the previous day's closing price. Index values like Nifty 50 and Sensex are also computed using closing prices of constituent stocks.
For corporate actions, the closing price on the ex-date determines the adjusted price used in settlement. For instance, when a company declares a dividend and the stock goes ex-dividend, the exchange adjusts the price band (and often the reference price for the next day) by subtracting the dividend amount from the previous closing price.
BSE follows a similar closing price methodology based on the weighted average of trades in the closing session. Some differences exist in the exact implementation between the two exchanges, which is why slight variations in reported closing prices between NSE and BSE are occasionally visible for the same security.