NoContAmts (FIX tag 518)

NumInGroupFIX 4.4group counter

NoContAmts (tag 518) is a NumInGroup field defined in FIX 4.4. It appears in 2 message types, always optionally. Its datatype is NumInGroup, which makes it a repeating-group counter: its value is the number of entries that follow, not a quantity in its own right.

At a glance

Tag: 518
Name: NoContAmts
Datatype: NumInGroup (int)
Dialects: FIX 4.4
Messages: 2

What the specification says

The number of Contract Amount details on an Execution Report message

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

A real message using tag 518

ExecutionReport · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	151
35	MsgType	8	Execution Report
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
37	OrderID	ORD-10042
17	ExecID	EXEC-88117
150	ExecType	0	New
39	OrdStatus	0	New
54	Side	1	Buy
151	LeavesQty	0
14	CumQty	1000000
6	AvgPx	1.09215
518	NoContAmts2 entries	2	repeating group
519	ContAmtType	1	Commission Amount (actual)
519	ContAmtType	1	Commission Amount (actual)
10	CheckSum	067

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 518 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
ExecutionReport	8	Optional	inside the ContAmtGrp component
TradeCaptureReport	AE	Optional	inside TrdCapRptSideGrp › ContAmtGrp

Wire format

The number of entries in the repeating group that follows. The next field on the wire is the group's delimiter tag. @boarteam/fix parses the value as a number and reports parse/invalid-int when it does not lex as one; the raw string is kept either way.

Read tag 518 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);// NoContAmts is a group counter, so the entries live on message.groups —// NOT on message.fields. message.fields[518] is undefined.const entries = message.groups[518] ?? [];for (const entry of entries) {  // entry.fields is keyed by tag; entry.groups holds nested groups}

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