Mechanism library · English
Why orders get rejected
Price bands, margins, lot sizes, quantity freezes, trade-to-trade segments — the mechanical reasons an order never reaches the market.
The price is outside the band
Every stock trades inside a price band the exchange sets — the price may move only so far in a day. An order whose limit price lies outside that band is rejected at the exchange, not by your broker. The band is a property of the stock, and it changes: the exchange widens and narrows bands, and a stock in a trade-to-trade segment gets different rules entirely.
A rejection is a fact about a gate, not a judgement of the trade.
| Gate | Typical reason the order never leaves |
|---|---|
| Risk engine | Velocity, size, or symbol restriction |
| Broker / RMS | Margin short, freeze, or product mismatch |
| Exchange | Price band, tick size, or freeze quantity |
| Algo-ID | Empty or unregistered identifier |
Margin is short
An order carries a margin requirement the moment it is placed. If the account does not hold the required margin — cash or pledged collateral — the order is rejected before it is routed. This is not a punishment and not a penalty; it is the exchange's risk system declining to accept an obligation the account has not funded.
Quantity rules
The exchange defines a lot size per instrument and a freeze quantity beyond which a single order is not accepted — both exist so that no single order can move a market accidentally. An order that is not a multiple of the lot size, or larger than the freeze limit, is rejected mechanically, regardless of how much money is in the account.
Rejections are information
A rejection tells you the market's machinery declined your order for a mechanical reason. The reason code says which one. Reading it instead of retrying blindly is the difference between fixing the order and hammering a rule that will not move. Every rejection reason on this platform is recorded and displayed as it arrived — never rewritten into something softer.