StopPx (FIX tag 99)

PriceFIX 4.4FIX 4.2FIX 5.0 SP2

StopPx (tag 99) is a Price field defined in FIX 4.4, FIX 4.2 and FIX 5.0 SP2. It appears in 8 message types, always optionally.

At a glance

Tag: 99
Name: StopPx
Datatype: Price (float)
Dialects: FIX 4.4, FIX 4.2 and FIX 5.0 SP2
Messages: 8

What the specification says

FIX 4.4

Price per unit of quantity (e.g. per share)

FIX 4.2

Price per share

FIX 5.0 SP2

Price per unit of quantity (e.g. per share)

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 99

NewOrderSingle · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	122
35	MsgType	D	Order – Single
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
11	ClOrdID	ORD-10042
54	Side	1	Buy
60	TransactTime	20240101-12:00:00.000
40	OrdType	1	Market
99	StopPx	1.09210
10	CheckSum	253

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 4.4 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 99 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	FIX 4.4	FIX 4.2	FIX 5.0 SP2	Where in the message
CrossOrderCancelReplaceRequest	t	Conditional	—	Optional	directly on the message body
ExecutionReport	8	Conditional	Optional	Optional	directly on the message body
MultilegOrderCancelReplace	AC	Conditional	—	Optional	directly on the message body
NewOrderCross	s	Conditional	—	Optional	directly on the message body
NewOrderList	E	Conditional	Optional	Optional	inside the ListOrdGrp component
NewOrderMultileg	AB	Conditional	—	Optional	directly on the message body
NewOrderSingle	D	Conditional	Optional	Optional	directly on the message body
OrderCancelReplaceRequest	G	Conditional	Optional	Optional	directly on the message body
TradeCaptureReport	AE	—	—	Optional	inside TrdCapRptSideGrp › TradeReportOrderDetail
TradeCaptureReportAck	AR	—	—	Optional	inside TrdCapRptAckSideGrp › TradeReportOrderDetail

Wire format

A decimal price. Precision is a venue convention, not a protocol rule, so compare the raw string when exactness matters. @boarteam/fix parses the value as a number and reports parse/invalid-float when it does not lex as one; the raw string is kept so precision and trailing zeros are never lost.

Read tag 99 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix44";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[99];field?.name;   // "StopPx"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a number

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix44

Try the decoder Source on GitHub