What is Periodic Call Auction and how does it work?

What Is Periodic Call Auction?

At FYERS, we follow the Periodic Call Auction (PCA) mechanism as mandated by SEBI and the stock exchanges to ensure transparent trading in illiquid securities—stocks that have very low daily trading activity. Instead of continuous trading, these securities are traded at specific intervals through call auctions. This system enhances price discovery, prevents price manipulation, and ensures a fair and transparent market process.

Eligibility Criteria

A stock is classified as illiquid and included in the Periodic Call Auction system if it meets all the following conditions:

  • Traded on fewer than 50 days in the last 12 months or has an average of fewer than 50 trades per day.
  • Has an average daily traded volume of less than 10,000 shares.
  • Not part of the NIFTY 500 or any derivative (F&O) segment.
  • Not listed on the SME platform or classified under Trade-for-Trade (T2T) settlement group.

These conditions are periodically reviewed by NSE and BSE. Eligible securities may be added to or removed from the PCA list based on liquidity changes.

How Does the Call Auction Work?

At FYERS, trading in PCA securities takes place through six call auction sessions during each trading day. Every session has three key stages—order placement, order matching, and a buffer period—allowing for controlled execution and transition between sessions.

Session No.Start TimeOrder PlacementOrder MatchingBuffer Period
109:30 AM09:30 – 10:1510:15 – 10:2310:24 – 10:30
210:30 AM10:30 – 11:1511:15 – 11:2311:24 – 11:30
311:30 AM11:30 – 12:1512:15 – 12:2312:24 – 12:30
412:30 PM12:30 – 01:1501:15 – 01:2301:24 – 01:30
501:30 PM01:30 – 02:1502:15 – 02:2302:24 – 02:30
602:30 PM02:30 – 03:1503:15 – 03:2303:24 – 03:30

Order Lifecycle

  • Order Placement Window: You can place, modify, or cancel orders during this phase.
  • Order Matching Window: The exchange matches buy and sell orders to determine an equilibrium price.
  • Buffer Period: Used for order confirmation and transitioning to the next session.

Matching Mechanism

All orders entered during the placement phase are pooled and processed together. The exchange identifies an equilibrium price—a single rate at which the maximum number of shares can be traded. This process ensures orderly execution and prevents volatility spikes.

  • Price-Time Priority: Orders at better prices are matched first. Among equal prices, earlier timestamps are prioritized.
  • Uniform Price: All trades during a session execute at one equilibrium price, ensuring fairness.
  • Partial Execution: If buy and sell volumes do not match fully, unexecuted portions may carry forward to the next session.

Example

Suppose “ABC Ltd” trades less than 8,000 shares daily with around 30 trades per day. It qualifies for the Periodic Call Auction mechanism. If you place a buy order during the 10:30–11:15 AM session, your order will execute only if there is a matching sell order during the 11:15–11:23 AM matching window.

Do’s and Don’ts

Here are some essential points to remember while trading illiquid securities under the PCA mechanism:

Do’sDon’ts
Check if a stock is currently under the PCA mechanism on NSE or BSE before placing orders.Do not expect immediate execution. Trades occur only in scheduled auction sessions.
Place your order early within a session to increase the chance of matching.Avoid using Intraday or high-frequency trading strategies. These are unsuitable for illiquid securities.
Monitor session timings and re-enter orders if unmatched.Do not modify or cancel orders during the matching or buffer windows.
Regularly check the official NSE Call Auction Stock List for updates.Do not assume orders carry forward across days. All unmatched orders are cancelled by end of day.

What If...

ScenarioExplanation
My order wasn’t executed during a sessionIt will automatically move to the next auction session unless cancelled manually.
My order remains unmatched throughout the dayIt will be cancelled automatically at the end of the day. You can re-enter it on the next trading day.
I want to buy or sell an illiquid stockYou must participate during the designated PCA windows. Continuous trading is not permitted for these securities.
Tip: For the latest list of securities under the Periodic Call Auction mechanism, visit the NSE Call Auction Stock List. You can also refer to the BSE FAQ document (PDF) for additional reference.
Important: The Periodic Call Auction is a SEBI-mandated process to ensure orderly price discovery in illiquid stocks. Orders can be placed only during active auction sessions and are executed as per exchange matching rules. Continuous trading is disabled for such securities.

Last updated: 03 Nov 2025

    • Related Articles

    • What is short selling?

      Short selling is a trade where you sell first and buy later to profit if the price falls. In India’s cash market with FYERS, this is an intraday-only activity: you must close (buy back) the same day. How does short selling work? Sell first: Place a ...

    • What Does Assignment Mean in Options?

      Assignment is when an option seller is obligated to fulfill the contract after the option is exercised. On NSE, options are European style, so exercise and any resulting assignment occur only on the expiry date. The settlement outcome depends on ...

    • What Happens If My Intraday Short Position or Delivery Obligation Isn’t Settled?

      If you sell shares without holding them (short sell) and don’t square off before market close, it may result in short delivery. At FYERS, we handle such settlements strictly as per exchange regulations. The exchange may conduct an auction to source ...

    • What Are Options?

      Options are derivative contracts that give the buyer a right but not an obligation, and the seller an obligation if exercised. A call gives the right to buy, and a put gives the right to sell at a preset strike price within a specified period. ...

    • What Is an Options Spread?

      An options spread uses two or more options on the same underlying to shape risk and reward. By buying one leg and selling another, you can cap potential loss, cap potential profit, reduce cost, or earn a premium with defined risk. Spreads are ...