MinLotSize (FIX tag 1231)

QtyFIX 5.0 SP2

MinLotSize (tag 1231) is a Qty field defined in FIX 5.0 SP2. It appears in 8 message types, always optionally.

At a glance

Tag: 1231
Name: MinLotSize
Datatype: Qty (float)
Dialects: FIX 5.0 SP2
Messages: 8

What the specification says

Minimum lot size allowed based on lot type specified in LotType(1093)

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

A real message using tag 1231

MarketDefinition · FIX 5.0 SP2

Tag	Field	Wire value	Meaning
8	BeginString	FIXT.1.1
9	BodyLength	134
35	MsgType	BU	MarketDefinition
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
1394	MarketReportID	EXAMPLE
1301	MarketID	XNAS
1234	NoLotTypeRules2 entries	2	repeating group
1093	LotType	1	Odd Lot
1231	MinLotSize	1000000
1093	LotType	1	Odd Lot
1231	MinLotSize	1000000
10	CheckSum	072

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 5.0 SP2 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 1231 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
DerivativeSecurityList	AA	Optional	inside DerivativeSecurityDefinition › MarketSegmentGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules
DerivativeSecurityListUpdateReport	BR	Optional	inside DerivativeSecurityDefinition › MarketSegmentGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules
MarketDefinition	BU	Optional	inside BaseTradingRules › LotTypeRules
MarketDefinitionUpdateReport	BV	Optional	inside BaseTradingRules › LotTypeRules
SecurityDefinition	d	Optional	inside MarketSegmentGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules
SecurityDefinitionUpdateReport	BP	Optional	inside MarketSegmentGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules
SecurityList	y	Optional	inside SecListGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules
SecurityListUpdateReport	BK	Optional	inside SecLstUpdRelSymGrp › SecurityTradingRules › BaseTradingRules › LotTypeRules

Wire format

A decimal quantity. Fractional quantities are legal, which is why this is a float family rather than an integer. @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 1231 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix50sp2";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[1231];field?.name;   // "MinLotSize"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-fix50sp2

Try the decoder Source on GitHub