RootPartySubID (FIX tag 1121)

StringFIX 5.0 SP2

RootPartySubID (tag 1121) is a String field defined in FIX 5.0 SP2. It appears in 8 message types, always optionally.

At a glance

Tag: 1121
Name: RootPartySubID
Datatype: String
Dialects: FIX 5.0 SP2
Messages: 8

What the specification says

PartySubID value within a root parties component. Same values as PartySubID (523)

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

A real message using tag 1121

TradeCaptureReport · FIX 5.0 SP2

Tag	Field	Wire value	Meaning
8	BeginString	FIXT.1.1
9	BodyLength	150
35	MsgType	AE	TradeCaptureReport
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
1116	NoRootPartyIDs1 entry	1	repeating group
1117	RootPartyID	EXAMPLE
1120	NoRootPartySubIDs2 entries	2	repeating group
1121	RootPartySubID	EXAMPLE
1121	RootPartySubID	EXAMPLE
32	LastQty	1000000
31	LastPx	1.09210
552	NoSides1 entry	1	repeating group
54	Side	1	Buy
10	CheckSum	241

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 5.0 SP2 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 1121 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	Requiredness	Where in the message
CrossOrderCancelReplaceRequest	t	Optional	inside RootParties › RootSubParties
CrossOrderCancelRequest	u	Optional	inside RootParties › RootSubParties
NewOrderCross	s	Optional	inside RootParties › RootSubParties
NewOrderList	E	Optional	inside RootParties › RootSubParties
QuoteRequest	R	Optional	inside RootParties › RootSubParties
QuoteRequestReject	AG	Optional	inside RootParties › RootSubParties
TradeCaptureReport	AE	Optional	inside RootParties › RootSubParties
TradeCaptureReportAck	AR	Optional	inside RootParties › RootSubParties

Wire format

Free-form text. Any byte except the SOH separator is legal, so values are not trimmed or case-folded on the wire. @boarteam/fix keeps the value as a string; format rules are checked by validate(), which reports validate/invalid-value rather than throwing.

Read tag 1121 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix50sp2";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[1121];field?.name;   // "RootPartySubID"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a string

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-fix50sp2

Try the decoder Source on GitHub