ReversalIndicator (FIX tag 700)

BooleanFIX 4.4

ReversalIndicator (tag 700) is a Boolean field defined in FIX 4.4. It appears in 2 message types, always optionally.

At a glance

Tag: 700
Name: ReversalIndicator
Datatype: Boolean (char)
Dialects: FIX 4.4
Messages: 2

What the specification says

Indicates a trade that reverses a previous trade.

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

A real message using tag 700

AllocationInstruction · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	135
35	MsgType	J	Allocation Instruction
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
70	AllocID	EXAMPLE
71	AllocTransType	0	New
626	AllocType	1	Calculated (includes MiscFees and NetMoney)
857	AllocNoOrdersType	0	Not specified
700	ReversalIndicator	N
54	Side	1	Buy
53	Quantity	1000000
6	AvgPx	1.09215
75	TradeDate	20240101
10	CheckSum	152

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 700 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
AllocationInstruction	J	Optional	directly on the message body
AllocationReport	AS	Optional	directly on the message body

Wire format

Y or N. Not 1/0, and not true/false. @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 700 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[700];field?.name;   // "ReversalIndicator"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a boolean

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