Order Entry

New Order Single (35=D)

Tag	Name	Type	Required	Description
11	ClOrderID	String	Y	Client order identifier for idempotency. UUID format is preferred.
18	ExecInst	Char	N	Execution instruction flags. Supported values: `6 = Post Only`, `E = Reduce Only` (IOC or FOK only)
38	OrderQty	Decimal	Y	Quantity of contracts to trade. Only whole-number quantities are supported.
40	OrdType	Char	Y	Supported values: `2 = Limit`
44	Price	Decimal	Y	Price per contract in fixed-point dollars, up to 4 decimal places.
50	SenderSubID	String	N	Clearing FCM sponsored access only. Header field identifying the operator for this order; printable ASCII, max 16 characters.
54	Side	Char	Y	Supported values: `1 = Buy (bid)`, `2 = Sell (ask)`
55	Symbol	String	Y	Market ticker
59	TimeInForce	Char	N	Supported values: `0 = Day`, `1 = Good Till Cancel`, `3 = Immediate Or Cancel`, `4 = Fill Or Kill`, `6 = Good Till Date`
126	ExpireTime	UTCTimestamp	C	Required when `TimeInForce = GTD`
448	PartyID	String	N	Only applicable for FCM entities. Customer-account or subaccount identifier.
452	PartyRole	Integer	N	Only applicable for FCM entities. Supported value: `24 = Customer Account`
453	NoPartyIDs	Integer	N	Only applicable for FCM entities. Currently only `1` is supported.
79	AllocAccount	Integer	N	Subaccount number (0-63). Alternative to NoPartyIDs.
526	SecondaryClOrdID	UUID	N	Order group identifier.
2964	SelfTradePreventionType	Integer	N	Supported values: `1 = Taker At Cross`, `2 = Maker`
21006	CancelOrderOnPause	Boolean	N	Cancel the order if trading pauses

SenderSubID<50> is captured on an ordinary NewOrderSingle and, per action, on OrderCancelRequest and OrderCancelReplaceRequest; it is ignored on RFQ quote acceptance. The operator on a NewOrderSingle sticks to the order: fills and other lifecycle reports emit it as the PartyRole=12 party. Cancel and Cancel/Replace acknowledgements instead emit the operator sent on that request — the operator who performed the action — falling back to the order’s creating operator when the request carried none. Do not send tag 50 on Logon: Kalshi rejects that Logon.

Example New Margin Order

8=FIXT.1.1|9=200|35=D|34=5|52=20230809-12:34:56.789|49=your-api-key|56=KalshiNR|
11=550e8400-e29b-41d4-a716-446655440000|38=10.00|40=2|54=1|55=BTC-PERP|44=19.5000|
59=1|10=123|

Order Cancel/Replace Request (35=G)

Used to modify an existing order without canceling it.

Supported Modifications

OrderQty: Increase or decrease the quantity. Increasing quantity forfeits queue priority.
Price: Change the limit price.
Expiry: Use Day (59=0) without 126 to expire at 11:59:59.999pm ET, set a future deadline with TimeInForce=GTD (59=6) and ExpireTime (126), or remove expiry with TimeInForce=GTC (59=1) and no 126. Expired deadlines, including the Unix epoch, are rejected.

Kalshi conventions for replace: Omitting both 59 and 126 preserves the order’s current expiry. This is a Kalshi-specific convention, rather than FIX’s Day default for omitted 59. To resend expiry explicitly, send 59=6 with the unchanged 126 for GTD, 59=0 without 126 for Day, or 59=1 without 126 for GTC. Send the current total OrderQty and price for an expiry-only amendment. Kalshi guarantees that an expiry-only amendment preserves FIFO queue position when price and quantity are unchanged.

Tag	Name	Type	Required	Description
11	ClOrderID	String	Y	Unique modification request identifier
37	OrderID	String	N	Kalshi exchange order identifier
38	OrderQty	Decimal	Y	New total quantity for the order
40	OrdType	Char	Y	Supported value: `2 = Limit`
41	OrigClOrdID	String	Y	ClOrderID of the order to modify
44	Price	Decimal	N	New fixed-point dollar price
50	SenderSubID	String	N	Clearing FCM sponsored access only. Header field identifying the operator performing this modification; printable ASCII, max 16 characters.
54	Side	Char	Y	Must match the original order side
55	Symbol	String	Y	Must match the original margin market ticker
59	TimeInForce	Char	N	`0`=Day sets expiry to 11:59:59.999pm ET and forbids ExpireTime; `1`=GTC clears expiry and forbids ExpireTime; `6`=GTD requires a future ExpireTime. Omit both tags to preserve expiry (Kalshi convention). Other values are not supported on replace.
126	ExpireTime	UTCTimestamp	C	Future expiration timestamp. Requires TimeInForce=GTD (`59=6`); cannot be sent alone or with Day/GTC. Expired timestamps, including the Unix epoch, are rejected.
448	PartyID	String	N	FCM customer-account or subaccount identifier
452	PartyRole	Integer	N	FCM party role
453	NoPartyIDs	Integer	N	FCM party count
79	AllocAccount	Integer	N	Subaccount number

Order Cancel Request (35=F)

Cancel all remaining quantity of an existing order.

Tag	Name	Type	Required	Description
11	ClOrderID	String	Y	Unique cancel request identifier
37	OrderID	String	N	Kalshi exchange order identifier
41	OrigClOrdID	String	Y	ClOrderID of the order to cancel
50	SenderSubID	String	N	Clearing FCM sponsored access only. Header field identifying the operator performing this cancel; printable ASCII, max 16 characters.
54	Side	Char	Y	Must match the original order side
55	Symbol	String	Y	Must match the original margin market ticker
448	PartyID	String	N	FCM customer-account or subaccount identifier
452	PartyRole	Integer	N	FCM party role
453	NoPartyIDs	Integer	N	FCM party count
79	AllocAccount	Integer	N	Subaccount number

Execution Report (35=8)

This message is sent by the exchange to reflect changes to an order’s state. Replaced reports confirm the resulting validity with TimeInForce=GTD (59=6) and the accepted ExpireTime (126), or TimeInForce=GTC (59=1) without 126 when there is no expiry. Kalshi stores Day orders as explicit deadlines, so their Replaced reports also use GTD with the end-of-day ET deadline; they do not echo the original Day value.

Tag	Name	Type	Required	Description
6	AvgPx	Decimal	Y	Average fill price in fixed-point dollars
11	ClOrderID	String	Y	ClOrderID from the last change-making request
14	CumQty	Decimal	Y	Total quantity filled so far
17	ExecID	String	Y	Unique sequenced identifier for this report message
30	LastMkt	String	C	Exchange index that produced the report.
31	LastPx	Decimal	C	Price of the last fill in fixed-point dollars
32	LastQty	Decimal	C	Quantity of the last fill
37	OrderID	String	Y	Exchange order identifier
38	OrderQty	Decimal	Y	Order quantity. By default this is `LeavesQty + CumQty`; if `21008=Y`, it remains the original order quantity.
39	OrdStatus	Char	Y	Current status of the order after this event
41	OrigClOrdID	String	C	Previous ClOrderID for replaced/canceled orders
44	Price	Decimal	C	Limit price in fixed-point dollars
54	Side	Char	Y	Original order side
55	Symbol	String	Y	Margin market ticker
58	Text	String	N	Human-readable result description
59	TimeInForce	Char	C	Present for Replaced reports: `6`=GTD when expiry exists (including Day deadlines), otherwise `1`=GTC.
60	TransactTime	UTCTimestamp	Y	Timestamp for the triggering event
103	OrdRejReason	Integer	C	Rejection reason when `ExecType = Rejected`
126	ExpireTime	UTCTimestamp	C	Expiration timestamp
150	ExecType	Char	Y	Why this execution report was sent
151	LeavesQty	Decimal	Y	Remaining quantity open for execution
448	PartyID	String	N	FCM customer-account identifier or the operator captured from SenderSubID
452	PartyRole	Integer	N	FCM party role: `24 = Customer Account`, `12 = Executing Trader`
453	NoPartyIDs	Integer	N	FCM party count. Up to 2 when both customer account and operator are present.
79	AllocAccount	Integer	C	Subaccount number
715	ClearingBusinessDate	LocalMktDate	C	Clearing date (`YYYYMMDD`). Each date covers the interval from 4:00 p.m. ET on the prior calendar day (inclusive) to 4:00 p.m. ET on that date (exclusive), including weekends and holidays. Present only for `ExecType = Trade`

Order Status (39)

New<0>: Active order, no fills
Partially Filled<1>: Some quantity filled
Filled<2>: Completely filled
Canceled<4>: Canceled
Replaced<5>: Order modified via Cancel/Replace
Pending Cancel<6>: Cancel pending
Rejected<8>: Order rejected
Pending New<A>: Order pending acceptance
Expired<C>: Time-in-force expired
Pending Replace<E>: Modification pending

With default settings, expiry-style system cancellations are reported as Canceled<4>. If 21012 (UseExpiredOrdStatus)=Y, expiry-style system cancellations emit Expired<C>.

Order Rejection Reasons (103)

Unknown symbol<1>
Exchange closed<2>
Order exceeds limit<3>
Too late to enter<4>
Stale order<5>
Duplicate order<6>
Unsupported order characteristic<11>
Incorrect quantity<13>
Unknown account<15>
Other<99>

Execution Types (150)

New<0>
Trade<F>
Canceled<4>
Replaced<5>
Rejected<8>
Expired<C>
Pending New<A>
Pending Cancel<6>
Pending Replace<E>

Text Field Values (58)

Common values include:

EXCHANGE_UNAVAILABLE
INTERNAL_ERROR
MARKET_ALREADY_CLOSED
MARKET_INACTIVE
MARKET_NOT_FOUND
SELF_CROSS_ATTEMPT
ORDER_ALREADY_EXISTS
EXCEEDED_PER_MARKET_RISK_LIMIT
EXCEEDED_ORDER_GROUP_RISK_LIMIT
ORDER_GROUP_NOT_FOUND
FOK_INSUFFICIENT_VOLUME
POST_ONLY_CROSS
ORDER_GROUP_CANCEL
TAKER_CANCEL_FOR_SELF_TRADE_PREVENTION
MAKER_CANCEL_FOR_SELF_TRADE_PREVENTION
IMMEDIATE_OR_CANCELLED
REDUCE_ONLY

OrderCancelReject (35=9)

Exchange-returned amend and cancel failures are returned as OrderCancelReject (35=9), not ExecutionReport.

Text (58)	CxlRejReason (102)
`INVALID_AMEND_QTY_FOR_ORDER`	Broker
`CANNOT_UPDATE_FILLED_ORDER`	Broker
`SELF_CROSS_ATTEMPT`	Invalid price increment

Position and Fee Information

When ExecType = Trade:

Tag	Name	Description
704	LongQty	Net long position after trade
705	ShortQty	Net short position after trade
136	NoMiscFees	Number of fees
137	MiscFeeAmt	Total fees in dollars
138	MiscFeeCurr	Currency (USD)
139	MiscFeeType	Exchange fees
891	MiscFeeBasis	Fee unit (always `ABSOLUTE<0>`)
880	TrdMatchID	Trade identifier
1057	AggressorIndicator	Taker/maker flag

Collateral Changes

Tag	Name	Description
1703	NoCollateralAmountChanges	Number of collateral changes
1704	CollateralAmountChange	Delta in dollars
1705	CollateralAmountType	Balance or payout

Party Information

Execution reports independently include the customer account when applicable and at most one operator entry (Executing Trader<12>). Which operator appears depends on the report type: fills and other order-lifecycle reports (expiration, IOC cancellation, and similar) carry the operator captured at order creation, while Cancel and Cancel/Replace acknowledgements carry the operator sent on the acting request, falling back to the creation operator when that request carried none. When both a customer-account entry and an operator entry are present, the customer-account entry comes first.

Tag	Name	Description
453	NoPartyIDs	Number of parties: one or two
448	PartyID	Customer-account or operator identifier
452	PartyRole	Customer Account<24> or Executing Trader<12>
79	AllocAccount	Subaccount number (0-63)

Rejection Reasons (102)

Too late to cancel<0>
Unknown order<1>
Other<99>

Mass Cancel Request (35=q)

Cancel all orders for the trading session. Only available on KalshiNR (NewOrderMode) sessions.

Tag	Name	Description
11	ClOrderID	Unique request ID
530	MassCancelRequestType	Cancel for session<6>

Mass Cancel Report (35=r)

Response to mass cancel request.

Tag	Name	Description
11	ClOrderID	Request ID
37	OrderID	Operation ID
531	MassCancelResponse	Success<6> or Rejected<0>
532	MassCancelRejectReason	If rejected

Individual ExecutionReports follow for each cancelled order.

Overview

REST

WebSockets

FIX

New Order Single (35=D)

Order Cancel/Replace Request (35=G)

Supported Modifications

Order Cancel Request (35=F)

Execution Report (35=8)

Order Status (39)

Order Rejection Reasons (103)

Execution Types (150)

Text Field Values (58)

OrderCancelReject (35=9)

Position and Fee Information

Collateral Changes

Party Information

Rejection Reasons (102)

Mass Cancel Request (35=q)

Mass Cancel Report (35=r)

​New Order Single (35=D)

​Order Cancel/Replace Request (35=G)

​Supported Modifications

​Order Cancel Request (35=F)

​Execution Report (35=8)

​Order Status (39)

​Order Rejection Reasons (103)

​Execution Types (150)

​Text Field Values (58)

​OrderCancelReject (35=9)

​Position and Fee Information

​Collateral Changes

​Party Information

​Rejection Reasons (102)

​Mass Cancel Request (35=q)

​Mass Cancel Report (35=r)

New Order Single (35=D)

Order Cancel/Replace Request (35=G)

Supported Modifications

Order Cancel Request (35=F)

Execution Report (35=8)

Order Status (39)

Order Rejection Reasons (103)

Execution Types (150)

Text Field Values (58)

OrderCancelReject (35=9)

Position and Fee Information

Collateral Changes

Party Information

Rejection Reasons (102)

Mass Cancel Request (35=q)

Mass Cancel Report (35=r)