Common Components

Kalshi’s FIX implementation uses FIXT.1.1 with application version FIX50SP2. Members on the Premier tier or above have FIX access by default.

FIX Dictionary

Download the Kalshi-specific FIX dictionary for import into your FIX engine:

Kalshi FIX Dictionary (XML)

If you are using a FIX engine such as QuickFIX/J, QuickFIX/N, or quickfix-go, the standard header and trailer fields below are managed automatically by the library. This section is primarily a reference for custom implementations or debugging.

Standard Header

Every FIX message begins with the following fields:

Tag	Name	Type	Required	Description
8	BeginString	String	Y	Always `FIXT.1.1`
9	BodyLength	Int	Y	Message length in bytes, from the tag after BodyLength up to (but not including) the CheckSum field. Must be the second field.
35	MsgType	String	Y	Identifies the message type. Must be the third field.
49	SenderCompID	String	Y	Your FIX API Key (UUID format) when sending; `Kalshi` when receiving.
56	TargetCompID	String	Y	Session identifier (e.g. `KalshiRT`, `KalshiNR`) when sending; your API key when receiving.
34	MsgSeqNum	Int	Y	Monotonically increasing sequence number, starting at 1.
52	SendingTime	UTCTimestamp	Y	Time the message was sent, in UTC. Format: `YYYYMMDD-HH:MM:SS.mmm`. Must be within 30 seconds of server time or the message is rejected (`SessionRejectReason=10`).
43	PossDupFlag	Boolean	N	`Y` if the message is a possible duplicate of a previously sent message (used during retransmission).
97	PossResend	Boolean	N	`Y` if the message may contain information that has already been sent under a different sequence number.
122	OrigSendingTime	UTCTimestamp	N	Original SendingTime of a message being resent. Required when `PossDupFlag=Y`.

Standard Trailer

Every FIX message ends with:

Tag	Name	Type	Required	Description
10	CheckSum	String	Y	Three-character checksum. Calculated by summing every byte in the message up to (but not including) the CheckSum field, then taking modulo 256. Always three digits, zero-padded (e.g. `007`).

Supported MsgTypes

Session-Level (all sessions)

MsgType	Name	Direction
A	Logon	Both
0	Heartbeat	Both
1	TestRequest	Both
2	ResendRequest	Both (KalshiRT, KalshiPT only)
3	Reject	Server -> Client
4	SequenceReset	Both (KalshiRT, KalshiPT only)
5	Logout	Both

Application-Level

Order Entry

MsgType	Name	Sessions	Direction
D	NewOrderSingle	KalshiNR, KalshiRT	Client -> Server
F	OrderCancelRequest	KalshiNR, KalshiRT	Client -> Server
G	OrderCancelReplaceRequest	KalshiNR, KalshiRT	Client -> Server
q	OrderMassCancelRequest	KalshiNR	Client -> Server
8	ExecutionReport	KalshiNR, KalshiRT, KalshiDC	Server -> Client
9	OrderCancelReject	KalshiNR, KalshiRT	Server -> Client
r	OrderMassCancelReport	KalshiNR	Server -> Client
j	BusinessMessageReject	All	Server -> Client

Order Groups

MsgType	Name	Sessions	Direction
UOG	OrderGroupRequest	KalshiNR, KalshiRT	Client -> Server
UOH	OrderGroupResponse	KalshiNR, KalshiRT	Server -> Client

Drop Copy

MsgType	Name	Sessions	Direction
U1	EventResendRequest	KalshiNR, KalshiDC	Client -> Server
U2	EventResendComplete	KalshiNR, KalshiDC	Server -> Client
U3	EventResendReject	KalshiNR, KalshiDC	Server -> Client

Historical replay on both KalshiNR and KalshiDC requires allowlisting for your user account. Contact institutional@kalshi.com to request access. After an EventResendRequest, the server replays the matching historical order updates as ExecutionReport (35=8) messages and then sends EventResendComplete (35=U2) or EventResendReject (35=U3).

Market Data

MsgType	Name	Sessions	Direction
V	MarketDataRequest	KalshiMD	Client -> Server
W	MarketDataSnapshotFullRefresh	KalshiMD	Server -> Client
X	MarketDataIncrementalRefresh	KalshiMD	Server -> Client
Y	MarketDataRequestReject	KalshiMD	Server -> Client
e	SecurityStatusRequest	KalshiMD	Client -> Server
f	SecurityStatus	KalshiMD	Server -> Client

Post Trade

MsgType	Name	Sessions	Direction
UMS	MarketSettlementReport	KalshiPT, KalshiRT	Server -> Client

RFQ

MsgType	Name	Sessions	Direction
R	QuoteRequest	KalshiRT, KalshiRFQ	KalshiRT: Client -> Server; KalshiRFQ: Server -> Client
b	QuoteRequestAck	KalshiRT	Server -> Client
S	Quote	KalshiRT, KalshiRFQ	KalshiRT: Server -> Client; KalshiRFQ: Client -> Server
AI	QuoteStatusReport	KalshiRFQ	Server -> Client
Z	QuoteCancel	KalshiRFQ	Client -> Server
U9	QuoteCancelStatus	KalshiRFQ	Server -> Client
AG	QuoteRequestReject	KalshiRT, KalshiRFQ	Server -> Client
UA	AcceptQuote	KalshiRT	Client -> Server
UC	AcceptQuoteStatus	KalshiRT	Server -> Client
U7	QuoteConfirm	KalshiRFQ	Client -> Server
U8	QuoteConfirmStatus	KalshiRFQ	Server -> Client
UE	RFQCancel	KalshiRT	Client -> Server
UB	RFQCancelStatus	KalshiRT	Server -> Client

REST

CF Benchmarks REST

WebSockets

FIX

FIX Dictionary

Standard Header

Standard Trailer

Supported MsgTypes

Session-Level (all sessions)

Application-Level

Order Entry

Order Groups

Drop Copy

Market Data

Post Trade

RFQ

​FIX Dictionary

​Standard Header

​Standard Trailer

​Supported MsgTypes

​Session-Level (all sessions)

​Application-Level

​Order Entry

​Order Groups

​Drop Copy

​Market Data

​Post Trade

​RFQ

FIX Dictionary

Standard Header

Standard Trailer

Supported MsgTypes

Session-Level (all sessions)

Application-Level

Order Entry

Order Groups

Drop Copy

Market Data

Post Trade

RFQ