Regulation Periodic Call Auction PCA Surveillance

Periodic Call Auction stocks

From WebNotes, a public knowledge base. Last updated 20 May 2026. Reading time ~4 min.

Periodic Call Auction (PCA) is a discrete-interval order-matching mechanism used by NSE / BSE for thinly traded or heavily surveilled stocks. Instead of continuous matching during market hours, PCA matches orders at scheduled intervals (typically every 30 minutes or hour), allowing price discovery in a controlled environment.

How PCA works

In a normal session:

Continuous matching of buy and sell orders throughout 09:15 to 15:30.
Real-time price discovery.

In PCA:

Order collection window (e.g., 09:15 to 09:45) where orders are accepted but not matched.
Matching event at the end of the collection window (09:45).
Next collection window opens (09:45 to 10:15).
Repeat throughout the session.

At each matching event, the exchange computes the price that maximises matched volume and executes all eligible orders at that price.

Which scrips are in PCA

PCA is used for:

Illiquid scrips with insufficient continuous-market activity to justify normal matching.
LT-ASM Stage 4 scrips (heavy surveillance).
GSM Stage 6 scrips.
Newly listed SME segment scrips (in some cases).
Scrips after a corporate action during a transitional period.

The exchange updates the PCA list daily.

Schedule of matching events

Typical PCA schedule (subject to update):

Auction window	Approximate timing
Auction 1	09:15 to 09:45
Auction 2	09:45 to 10:15
Auction 3	10:15 to 10:45
…	(continuing every 30 min)
Last auction	~15:00 to 15:30

About 12 auction windows during a normal session. Each window has order collection, matching, then transition to next window.

Pricing in PCA

At the matching event:

The exchange aggregates all buy and sell orders received during the collection window.
The price is calculated to maximise the volume of trades that can match.
Orders that match at that price execute; unmatched orders carry over to the next window or get cancelled (depending on rules).

This is similar to the pre-open session auction mechanic for headline equities, applied throughout the day.

Effect on retail traders

Slower price discovery

Prices only update at matching events. Within a window, the displayed LTP is the last matched price, not a live tick. This can be confusing for retail users used to continuous quotes.

Limit orders are the norm

In PCA, market orders are typically not allowed (no continuous market price to match against). Limit orders specify a price; they wait for the next auction window.

Slippage characteristics differ

Slippage in PCA is determined by the supply / demand imbalance at the matching event, not by intra-window movement. A large order may impact the auction-cleared price significantly.

Limited intraday strategies

Most intraday strategies depending on continuous matching (scalping, momentum trading) are infeasible in PCA. Only longer-term delivery trades work.

Implications for portfolio management

For investors holding a scrip that moves to PCA:

Exit liquidity is limited to the matching events.
Large sales may require multiple windows.
Price discovery is less granular; the exit price may be unpredictable.

For prospective buyers:

PCA scrips are generally low-quality or high-risk; consider whether to participate.
Limit orders allow you to specify exact price; if the auction-cleared price differs, you may not match.

Difference from auction market

Concept	Periodic Call Auction (PCA)	Auction market
Trigger	Surveillance restriction or illiquidity	Short-delivery resolution
Frequency	Throughout the day	Once daily (14:00 to 15:00 NSE)
Eligible scrips	Specific list	All scrips with short delivery
Order matching	Periodic	Continuous within window

The two are distinct mechanisms despite the similar name.

How Zerodha handles PCA scrips

Zerodha Kite places PCA orders in the order ticket flow:

Order ticket adapts to show the PCA window.
Limit orders are the default; market orders may be restricted.
The order book shows pending orders by window, not as a continuous feed.

For retail clients on PCA scrips, Zerodha recommends:

Use limit orders.
Allow time for matching windows.
Don’t expect immediate execution.

External references

References

SEBI, Periodic Call Auction framework for illiquid scrips, circular dated 17 February 2013 and updates.
NSE India, PCA operational guidelines, nseindia.com.
BSE India, PCA segment rules, bseindia.com.

Reviewed and published by

WebNotes Editorial Team

The WebNotes Editorial Team covers Indian capital markets, payments infrastructure and retail investor procedures. Every article is fact-checked against primary sources, principally SEBI circulars and master directions, NPCI specifications and the official support documentation published by the intermediary in question. Drafts go through a second-pair-of-eyes review and a separate compliance read before publication, and revisions are tracked against the SEBI and NPCI rule changes referenced in the methodology section.

Last reviewed: 20 May 2026
Conflicts of interest: WebNotes is independent. No relationship with any broker, registrar or bank named in this article.