PSX has two different circuit-breaker mechanisms. A scrip-based circuit breaker sets the highest and lowest prices at which a security may trade; an index-based market halt can suspend all equity and equity-based derivative markets after the KSE-30 stays at a 5% move for five consecutive minutes. The first is calculated security by security. The second is triggered by the index. They are separate rules in current PSX Regulations, Chapter 19.3–19.4.
A price cap is not a market-wide halt
In the general case, the per-scrip rule limits how far a security’s price may move from its previous day’s closing price. The index rule watches the KSE-30 and, if its trigger conditions are met, halts trading across equity and equity-based derivative markets. A security reaching its own cap does not by itself mean that the whole market has halted; likewise, an index halt is not a new percentage cap for each listed security.
How the per-scrip limit is calculated
As a general rule, Rule 19.3 applies a security-wise circuit breaker separately for each market, except the Stock Index Futures Market and Index Option Market. The rule describes a starting limit of 7.5% or Re.1, whichever is greater, from the security’s previous-day closing price, increasing by 0.5 percentage points every 15th day (or at another time PSX notifies) until reaching 10% or Re.1, whichever is greater. PSX’s 2024 implementation notice says that phase-in was completed on 22 July 2024; it is not an ongoing step-up today.
Rule 19.3 also has exceptions to that general calculation. ETFs use NAV-related bases, including a weighted-average limit when their underlying securities are subject to both the rupee and percentage limits. On a Right Allotment Letter’s first trading day, the notional price is based on the underlying security’s prior close less the payable amount; if that amount equals or exceeds the prior close, the notional price is the underlying security’s tick size. Other new securities have separate offer-price or book-building-price rules. Check the applicable subclause before applying the general previous-close formula to one of these cases.
The rule says the calculated price is rounded to the nearest tick. Trading is allowed up to the upper and lower circuit prices, but no trade in the respective security is allowed beyond them. Because the rupee floor and tick rounding both affect the price calculation, the percentage shown for a particular security need not look exactly like the headline percentage.
PSX’s live Circuit Breakers page separates securities into Upper Cap and Lower Cap sections and lists each symbol with its LDCP and market data. The page is a live view of securities at the caps; it should not be read as one universal percentage that applies identically to every displayed security.
What changed in 2024
PSX Notice PSX/N-477, dated 20 May 2024, described a phased increase beginning 27 May and completing on 22 July 2024. Its implementation schedule moved the stated percentage in half-point steps from 7.5% to 10%, while retaining the Re.1 floor. The notice names Regular, Futures and SIFC market symbols as covered by that implementation and says there was no change then to SQR and FUTSQR circuit breakers. Those are the product classes the notice specifies; it is not a basis for extending that historical implementation statement to every PSX market or symbol.
How the KSE-30 market halt works
Under Rule 19.4, PSX sets a separate index-based trigger when the KSE-30 moves 5% either way from its previous trading day’s closing index value. If it continues to trade at 5% above or below that reference for five consecutive minutes, trading in all securities is halted for a duration specified by PSX.
When the halt is imposed, all equity and equity-based derivative markets are suspended. The market has a five-minute pre-open before reopening. The rule does not set a single fixed halt length: PSX specifies the duration. It also provides a close-of-market exception: the index-based halt does not apply if the KSE-30 moves beyond 5% during the period before close that PSX specifies.
Why older explanations may differ
The current rulebook is the reference for the rules in force. Older material can describe a different design: for example, PSX/N-117 in 2021 was a public consultation proposal for two index-halt stages at 5% and 7.5%, not the current text of Rule 19.4. Treating that proposal as the present rule can make stale summaries misleading.
For adjacent background, see PSX market types, the KSE-100 explanation and PSX company coverage; the position-sizing tool is separate and does not affect exchange circuit limits.
Primary sources
- PSX Regulations, updated 9 February 2026 — Chapter 19, Rules 19.3–19.4: security-wise limits, rounding, trading boundaries, KSE-30 halt trigger, affected markets, pre-open and close exception.
- PSX Notice PSX/N-477, 20 May 2024 — phase-in dates and implementation scope for Regular, Futures and SIFC symbols; SQR and FUTSQR were unchanged at that stage.
- PSX DPS Circuit Breakers — live per-symbol display of upper and lower caps.
Research, not advice. This post explains the published exchange rules and makes no investment recommendation or forecast. Rules and displayed market data can change; consult PSX’s current material for the latest details.