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Price bands and trading halts
How a rolling reference constrains executions, and what triggers the city's temporary LULD pause.
Last updated: 2026-09-20
A rolling band, not a daily ceiling
MockTradeCity's Limit Up-Limit Down mechanism, or LULD, places boundaries around a rolling reference price during Regular trading. It is not a fixed daily percentage limit around previous close. The reference can move as eligible trades accumulate, so a company's total daily move can exceed one band's width while each execution still respects the boundary in force at its own moment. The daily range and the current band describe different intervals.
The LULD mechanism applies during the Regular session, from 9:30 a.m. to 4:00 p.m. Eastern Time. Overnight, Pre-market and After-hours use their other order-price protections without this Regular-session LULD pause. These are the city's implemented rules for fictional shares. Familiar terminology does not mean every parameter or operational detail matches a real exchange. Market state and the order ticket determine which protections apply to a specific request.
The applicable width has exceptions
For stocks whose previous Regular close is above 3 CC, the usual band is five percent for the city's Tier 1 group and ten percent for Tier 2. Lower-priced stocks use different parameters: previous closes from 0.75 through 3 CC select a twenty percent band, while prices below 0.75 CC use the smaller of a seventy-five-percent offset and 0.15 CC. Price-tick rounding also constrains the exact boundary.
During the final twenty-five minutes of Regular trading, the band doubles for Tier 1 stocks and stocks whose previous close is no more than 3 CC. Previous close selects the day's parameter category, while the rolling reference supplies the price around which the band is drawn. A percentage appearing in a halt message therefore describes the applicable condition, and cannot always identify a company's tier by itself without considering those exceptions.
The reference moves on eligible trades
The rolling reference uses eligible trades from a five-minute lookback, with a minimum trade quantity of 100 shares for this calculation. It does not update after every small execution. Refresh checks are separated by at least thirty seconds, and a candidate reference must differ sufficiently from the existing reference before it replaces it. These rules smooth the boundary's movement without changing the price or quantity of any trade already recorded.
Resting Limit orders and market-maker quotes also face band constraints. An IOC limit can express a wider maximum or minimum without granting permission to execute outside the active band. That distinction separates an order's submitted boundary from an actual fill. The Order book, rolling reference and execution protections work together: a permissive-looking ticket limit alone cannot compel an out-of-band trade or force the public latest price to jump beyond the permitted range.
A sustained boundary state triggers the pause
A trade touching a boundary is not enough by itself. The city detects a limit state when the best Bid sits at the upper band or the best Ask sits at the lower band under the engine's boundary conditions. If that state persists continuously for fifteen seconds, it triggers a five-minute trading halt. During the limit state, the reference and band are held rather than quietly widening as the closing-period schedule changes.
If the book leaves the boundary before the required duration, the limit-state timer clears and normal reference processing resumes. During a triggered halt, the company does not accept new orders or produce executions. Existing orders are not canceled merely because the halt began, though their ordinary expiry still matters. The automatic pause has an expected resumption time. A separately imposed administrative halt can instead have a stated reason without a fixed five-minute duration.
Where to inspect a halt in the city
The company page's status identifies whether the stock is trading, under an automatic halt or under another suspension. The halt explanation provides its reason and expected recovery time when applicable. That status is firmer evidence than a quiet chart: an interval with no executions can also result from inactivity, and an aggregated chart need not draw every empty minute as a visible gap. A pause itself never creates a new traded price.
Order responses explain when the company's current state prevents submission. Existing order records show what remains open or has expired, and the trade list shows executions before and after the interruption. Market rules provides the published protections. Together these views distinguish a temporary market restriction from a personal account problem or an unfilled price limit. The same restriction applies to players, virtual participants and market makers, all trading the city's fictional shares with City Coin.