IOIID (FIX tag 23)

StringFIX 4.4FIX 4.2

IOIID (tag 23) is a String field defined in FIX 4.4 and FIX 4.2. It appears in 8 message types and is required in 1 of them. FIX 4.2 calls this field IOIid; the tag number is unchanged, so the two are the same field on the wire.

Also known as IOIid

FIX 4.2 calls tag 23 IOIid. It is the same field on the wire — only the name changed — so a message encoded by either side interoperates.

At a glance

Tag: 23
Name: IOIID
Datatype: String
Dialects: FIX 4.4 and FIX 4.2
Messages: 8

What the specification says

Unique identifier of IOI message. (Prior to FIX 4.1 this field was of type int)

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

A real message using tag 23

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
23	IOIID	EXAMPLE
10	CheckSum	161

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 23 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	Where in the message
CrossOrderCancelReplaceRequest	t	Conditional	—	directly on the message body
IOI	6	Required	Required	directly on the message body
MultilegOrderCancelReplace	AC	Conditional	—	directly on the message body
NewOrderCross	s	Conditional	—	directly on the message body
NewOrderList	E	Conditional	Optional	inside the ListOrdGrp component
NewOrderMultileg	AB	Conditional	—	directly on the message body
NewOrderSingle	D	Conditional	Optional	directly on the message body
QuoteResponse	AJ	Optional	—	directly on the message body

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 23 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[23];field?.name;   // "IOIID"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