Commission (FIX tag 12)

AmtFIX 4.4FIX 4.2

Commission (tag 12) is an Amt field defined in FIX 4.4 and FIX 4.2. It appears in 16 message types, always optionally.

At a glance

Tag: 12
Name: Commission
Datatype: Amt (float)
Dialects: FIX 4.4 and FIX 4.2
Messages: 16

What the specification says

FIX 4.4

Commission. Note if CommType (3) is percentage, Commission of 5% should be represented as .05.

FIX 4.2

Commission. Note if CommType is percentage, Commission of 5% should be represented as .05.

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

A real message using tag 12

NewOrderSingle · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	124
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
12	Commission	125000.00
10	CheckSum	075

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 12 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
AllocationInstruction	J	Optional	Optional	inside AllocGrp › CommissionData
AllocationReport	AS	Optional	—	inside AllocGrp › CommissionData
BidResponse	l	Optional	Required	inside BidCompRspGrp › CommissionData
Confirmation	AK	Optional	—	inside the CommissionData component
CrossOrderCancelReplaceRequest	t	Optional	—	inside SideCrossOrdModGrp › CommissionData
ExecutionReport	8	Optional	Optional	inside the CommissionData component
MultilegOrderCancelReplace	AC	Optional	—	inside the CommissionData component
NewOrderCross	s	Optional	—	inside SideCrossOrdModGrp › CommissionData
NewOrderList	E	Optional	Optional	inside ListOrdGrp › CommissionData
NewOrderMultileg	AB	Optional	—	inside the CommissionData component
NewOrderSingle	D	Optional	Optional	inside the CommissionData component
OrderCancelReplaceRequest	G	Optional	Optional	inside the CommissionData component
Quote	S	Optional	—	directly on the message body
QuoteResponse	AJ	Optional	—	directly on the message body
QuoteStatusReport	AI	Optional	—	directly on the message body
TradeCaptureReport	AE	Optional	—	inside TrdCapRptSideGrp › CommissionData

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 12 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[12];field?.name;   // "Commission"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