Nested3PartyIDSource (FIX tag 950)

charFIX 4.4

Nested3PartyIDSource (tag 950) is a char field defined in FIX 4.4. It appears in 2 message types, always optionally.

At a glance

Tag: 950
Name: Nested3PartyIDSource
Datatype: char
Dialects: FIX 4.4
Messages: 2

What the specification says

PartyIDSource value within a "third instance" Nested repeating group. Same values as PartyIDSource (447)

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

A real message using tag 950

NewOrderMultileg · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	188
35	MsgType	AB	New Order - Multileg
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
11	ClOrdID	ORD-10042
78	NoAllocs1 entry	1	repeating group
79	AllocAccount	EXAMPLE
948	NoNested3PartyIDs2 entries	2	repeating group
949	Nested3PartyID	EXAMPLE
950	Nested3PartyIDSource	1
949	Nested3PartyID	EXAMPLE
950	Nested3PartyIDSource	1
54	Side	1	Buy
555	NoLegs1 entry	1	repeating group
600	LegSymbol	EXAMPLE
60	TransactTime	20240101-12:00:00.000
40	OrdType	1	Market
10	CheckSum	210

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 950 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
MultilegOrderCancelReplace	AC	Conditional	inside PreAllocMlegGrp › NestedParties3
NewOrderMultileg	AB	Conditional	inside PreAllocMlegGrp › NestedParties3

Wire format

A single character. Most char fields are enumerated, so the value is one of a fixed set rather than arbitrary text. @boarteam/fix keeps the value as a string and, for enumerated fields, reports validate/value-not-in-enum when it is not a defined value.

Read tag 950 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[950];field?.name;   // "Nested3PartyIDSource"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-fix44

Try the decoder Source on GitHub