Why a stock freezes: the reservation thresholds

Two limits, not one

The STATIC limit is measured against the reference price — yesterday's close. The DYNAMIC limit is measured against the last traded price, and is ± 2 %. A stock can therefore be reserved without reaching its static limit, simply for moving too fast.

The reservation lasts 10 minutes, then trading resumes with an auction. A day-valid limit order placed outside the thresholds is rejected — article 92 of the exchange's general regulation.

The threshold depends on the quotation group

Every stock trades in a group, printed in the official bulletin. The group sets the threshold, and how the stock trades — continuously or by auctions.

Group	Static threshold	Trading	Stocks
11	± 6 %	continuous	47
12	± 4.5 %	auctions	16
99	± 4.5 %	auctions	12

How we know

The exchange publishes no simple table of thresholds by group. So we MEASURED it on our own prices, by asking the only question that settles it: what goes beyond? A threshold that exists is never crossed — and the largest move observed gives it to the second decimal.

Group	Moves observed	Largest observed
11	6,125	6.000 %
12	1,328	4.500 %
99	784	4.500 %

Measured over 8,237 moves between consecutive sessions, from 15/05/2023 to 17/09/2026. The move used is the one the exchange publishes, not a ratio of two closes. This measurement corrected our own table: the auction groups were recorded at 4%, they are at 4.5%.