FairValue (FIX tag 406)

AmtFIX 4.4FIX 4.2FIX 5.0 SP2

FairValue (tag 406) is an Amt field defined in FIX 4.4, FIX 4.2 and FIX 5.0 SP2. It appears in 2 message types, always optionally.

At a glance

Tag: 406
Name: FairValue
Datatype: Amt (float)
Dialects: FIX 4.4, FIX 4.2 and FIX 5.0 SP2
Messages: 2

What the specification says

Used in EFP trades

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

A real message using tag 406

BidResponse · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	123
35	MsgType	l	Bid Response (lowercase L)
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
420	NoBidComponents2 entries	2	repeating group
12	Commission	125000.00
406	FairValue	125000.00
12	Commission	125000.00
406	FairValue	125000.00
10	CheckSum	231

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 406 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
BidRequest	k	Optional	Optional	Optional	inside the BidDescReqGrp component
BidResponse	l	Optional	Optional	Optional	inside the BidCompRspGrp component

Wire format

A decimal monetary amount, in the currency named by the message's currency field. @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 406 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[406];field?.name;   // "FairValue"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