The Additional Surveillance Measure (ASM) is a framework under which stock exchanges, together with the market regulator, the Securities and Exchange Board of India (SEBI), place extra trading conditions (mainly higher margins, and in stricter stages delivery-only trading) on stocks showing unusual price movement or trading activity. It is one of the surveillance measures designed to cool down speculation before ordinary investors get hurt.
Why would a stock enter ASM?
Exchanges continuously screen stocks against objective criteria. Things like how sharply the price has moved over recent weeks, how concentrated the trading is among a few clients, and how volatile the stock has been compared to the broader market. A stock that trips these filters gets shortlisted into ASM. The criteria are published by the exchanges and revised from time to time, so the framework stays mechanical rather than a judgement call on any one company.
The key point: ASM entry is triggered by trading behaviour, not by a finding of wrongdoing. A perfectly sound company can enter ASM simply because its stock ran up very fast.
What are long-term and short-term ASM?
ASM comes in two flavours:
- Short-term ASM catches stocks with a sudden, recent burst of unusual activity, a sharp spike over days or a few weeks. Stocks typically move through it quickly.
- Long-term ASM applies to stocks whose unusual behaviour has persisted over months. It has multiple stages, and a stock can be moved to stricter stages if the behaviour continues, or reviewed back out if it normalises.
Each stage tightens the trading conditions a notch. You don't need to memorise the stage table. What matters is knowing that "Stage IV" means tighter conditions than "Stage I", and that the exchange reviews and re-grades stocks on a set schedule.
What changes for me when a stock I trade enters ASM?
- Higher margins. The exchange raises the margin rate on the stock, in stricter stages up to the full trade value. In practice that means your broker collects much more money upfront, and leverage on the stock disappears.
- Possible move to Trade-to-Trade. In the stricter stages a stock can be shifted to the T2T segment, where every trade must be settled by delivery. See What is a Trade-to-Trade (T2T) stock, and how can I trade it?. That's also why you may find you can't place an Intraday order on some stocks.
- Extra scrutiny. ASM stocks stay on a published watchlist, which itself makes traders more careful.
Say Arjun holds 200 shares of Kaveri Motors, which enters long-term ASM after a steep rally. Nothing happens to his existing holding. He can continue to hold or sell it normally. But if he wants to buy more, he'll now pay the higher margin, and if the stock later moves to T2T, any new buy must be a full-payment Delivery order.
Is ASM a signal to sell?
No. ASM is a flag, not a verdict. It tells you the stock's recent trading pattern was unusual enough for the exchange to add guardrails. Some ASM stocks are genuine businesses in the middle of a re-rating; others are being pumped. The framework doesn't distinguish. It just makes speculating in the stock expensive, which protects you from being the last buyer in a frenzy. Treat ASM entry as a prompt to re-check why you own or want the stock.
Things to keep in mind
- ASM applies extra conditions to new trades; it doesn't freeze or take away shares you already hold.
- Exchanges review ASM lists on a regular cycle. Stocks move between stages and exit the framework, so check the current list rather than an old screenshot.
- The exact entry criteria, stage structure, and margin percentages are exchange-set and revised periodically; don't assume last year's numbers still apply.
- Higher margins protect you from over-leveraging into a volatile stock, but they don't cap how far the price itself can fall.
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