Circuit Filters – The Market’s Emergency Brakes

1. Introduction Ever seen a stock suddenly stop trading for the day after a sharp move? That’s likely because it hit a circuit filter. This mechanism is rarely talked about in-depth, but it plays a vital role in maintaining market stability, especially in volatile conditions. 2. What Are Circuit Filters? Circuit filters are price bands set by the stock exchanges within which a stock is allowed to move during a trading session. If the stock hits this upper or lower limit, trading gets halted or restricted. These are known as: Upper Circuit: Maximum allowable price rise in a day Lower Circuit: Maximum allowable price fall in a day It’s like a “speed governor” to prevent irrational, emotional or manipulative moves. 3. How Are Circuit Limits Decided? For most stocks, daily price bands are set at: 2%, 5%, 10%, 20% Depending on: Volatility history Market cap Liquidity SEBI/exchange discretion Highly liquid and large-cap stocks (like Reliance, TCS) often do not have fixed circuit limits because they are in the derivatives segment, where circuit control happens through other checks like dynamic price bands and position limits. 4. What Happens When a Stock Hits a Circuit? If a stock hits its circuit: Trading is paused or halted In many cases, trading resumes after a cooling-off period (15 mins or more) New circuit limits may be applied for the rest of the session For F&O stocks, there’s no circuit per se — but MWPL limits (Market-Wide Position Limits) and volatility filters act as indirect controls. 5. Why Are Circuit Filters Important? They help in: Controlling excessive speculation Preventing manipulation Providing time for price discovery Avoiding panic situations after major news or events Without them, stocks could be subject to flash crashes or pump-and-dump scenarios.