Order Entry

Understand what an order is, how time in force, post-only, and self-trade prevention shape it, and how to place, amend, and cancel orders.

An order is an instruction to buy or sell YES contracts in one market at a limit price. It belongs to one account, carries your own client_order_id for correlation, and is identified by the exchange-assigned order_id once accepted. See Markets and Trading for YES-side pricing and units.

Time in Force

Value	Meaning
`gtc`	Good till canceled. Rests until it fills or you cancel it.
`day`	Rests until the end of the trading day.
`gtt`	Good till time. Rests until the instant you set as `expires_at`, then expires.
`ioc`	Immediate or cancel. Fills what it can on arrival; the rest is canceled.
`fok`	Fill or kill. Fills completely on arrival or is canceled entirely.

An order read back from the exchange can also report unknown when it was placed through another channel with a time in force the exchange does not model. unknown is never accepted when placing an order.

Post-Only

A post-only order only ever adds liquidity. If it would cross the book on placement, the exchange rejects it instead of trading. Post-only cannot be combined with ioc or fok.

Self-Trade Prevention

Orders placed under the same member never trade with each other, whichever user or account placed them. self_trade_prevention_type on the incoming order chooses which order gives way when it would match one of your member’s resting orders:

Value	Behavior
`placed`	Cancels the incoming order when it would self-trade. The resting order stays open. This is the default.
`resting`	Cancels the conflicting resting order and lets the incoming order continue matching.

Self-trade prevention cannot be disabled.

Order Status

Status	Meaning
`resting`	Open on the book with nothing filled yet.
`partially_filled`	Open on the book with some quantity filled.
`filled`	Completely filled.
`canceled`	Canceled before filling completely.
`expired`	Its time in force ended before it filled completely.
`rejected`	Rejected by the exchange; `rejection_reason` says why.

Rejection Reasons

Reason	Meaning
`duplicate_client_order_id`	The `client_order_id` was already used on this account.
`self_trade_prevented`	The order would have traded against your member’s own order.
`market_closed`	The market is not open for trading.
`insufficient_funds`	The account lacks the balance to carry the order.
`price_out_of_bounds`	The price is outside the market’s limits.
`quantity_out_of_bounds`	The quantity or notional is outside the market’s limits.
`post_only_would_cross`	A post-only order would have traded on arrival.
`no_liquidity`	Nothing was available to trade against.
`quote_unavailable`	The quote named by an accept no longer exists or has lapsed.
`quote_terms_mismatch`	The accept’s side, price, or quantity did not match the quote.
`quote_already_accepted`	The quote or its RFQ is already in last look.
`rate_limited`	The exchange’s global rate limit was exceeded.
`expires_at_invalid`	A `gtt` order’s `expires_at` had already passed when the exchange received it.
`exchange_rejected`	The exchange rejected the order for a reason UDX does not classify.

Amend and Cancel

An amendment changes a resting order’s price, quantity, or both, in place. The new quantity is the total, not a delta, and must exceed the quantity already filled. Queue priority is preserved only when the quantity decreases at an unchanged price; any other change moves the order to the back of its price level.

A cancellation ends one resting order. A bulk cancellation ends every open order the credential can act for, optionally narrowed to one market or to named accounts; orders that fill while the cancellation is in flight are unaffected. A bulk cancellation is complete once a read of your working orders, those resting or partially_filled, returns none.