No Price Limits and the Volatility Control Mechanism (VCM)

No daily price limit

Hong Kong has no price limit: good or bad news can be fully priced in within a day, and single-day moves of tens of percent aren't unusual.

VCM: cool off for 5 minutes first

Some large stocks are covered by the Volatility Control Mechanism (VCM): if the price moves too far from the reference price of 5 minutes earlier within a short time, a 5-minute cooling-off period starts in which trades can only happen inside a set band; after that, trading carries on as normal.

No cap on a day's loss

With no price limit to cushion the fall, you can lose a lot in one day. In Hong Kong stocks, keep position sizes in check and use a stop-loss when needed, though on a gap a stop order may fill at a worse price.

Key takeaways

• Hong Kong has no price limits: good or bad news can be fully priced in within a day, and single-day moves of tens of percent aren't unusual.
• Some large stocks are covered by the Volatility Control Mechanism (VCM): if the price moves too far from the reference price of 5 minutes earlier, a 5-minute cooling-off starts in which trades can only happen inside a set band.
• The VCM doesn't stop the price from changing; it stretches a violent instant into a few minutes, and trading resumes as normal when the cooling-off ends.
• No price limits also means stop-losses and position sizing matter more: there's no cap on a day's loss.

Try it yourself

You can do these exercises in this lesson's interactive simulation:

1. In the first simulator, drag “News shock” to +30% and play: how many days to reach fair value? How does that compare with the A-share main board?
2. Press ▶ in the VCM simulator: at which minute does the cooling-off start? Can trades go outside the band during it?
3. Set the “sudden jump” to +8%: does it still trigger VCM? Why?
4. Change the jump to −25%: where does the price go after the cooling-off? Did VCM change the final direction?

Quiz and explanations

1. How far can a Hong Kong stock move in a day at most?

Answer: There's no daily price limit.Hong Kong stocks have no daily price limit, so a stock can swing a lot within a day.

2. What happens during a VCM cooling-off period?

Answer: For 5 minutes, trades can only happen within a band around the reference price.Once the VCM triggers, a 5-minute cooling-off starts in which trades must fall inside a set band; normal trading resumes afterwards.

3. Big news suddenly raises a stock's fair value by 30%. What's most likely?

Answer: The Hong Kong stock may get there the same day, while the A-share main-board stock needs several limit-up days.A-share main-board stocks can rise at most 10% a day, so it takes several days; Hong Kong has no price limit, so it can be fully priced in the same day.

Terms in this lesson

• price limit (Price Limit): Some markets cap how far a stock can move in a day (±10% for most Chinese main-board stocks); hitting the cap is limit-up, hitting the floor is limit-down.
• stop-loss (Stop Loss): Automatically closes a position when price moves against you to a preset level, capping your maximum loss.
• Volatility Control Mechanism (VCM) (Volatility Control Mechanism): A cooling-off period Hong Kong applies to some large stocks: if the price moves too far from the reference price within a few minutes, a 5-minute cooling-off starts in which trades can only happen inside a set price band.
• volatility interruption (Volatility Interruption): When a stock's price moves too far from a reference price in a short time, the exchange pauses continuous matching for a few minutes and switches to a call auction or a limited price band, so prices can't spin out of control in an instant.