DiscretionInst (FIX tag 388)

charFIX 4.4FIX 4.2FIX 5.0 SP2

DiscretionInst (tag 388) is a char field defined in FIX 4.4, FIX 4.2 and FIX 5.0 SP2. It appears in 8 message types, always optionally. It is an enumerated field with 7 defined values.

At a glance

Tag
388
Name
DiscretionInst
Datatype
char
Dialects
FIX 4.4, FIX 4.2 and FIX 5.0 SP2
Messages
8
Valid values
7

What the specification says

FIX 4.4

Code to identify the price a DiscretionOffsetValue (389) is related to and should be mathematically added to

FIX 4.2

Code to identify the price a DiscretionOffset is related to and should be mathematically added to.

FIX 5.0 SP2

Code to identify the price a DiscretionOffsetValue (389) is related to and should be mathematically added to.

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

A real message using tag 388

NewOrderSingle · FIX 4.4
TagFieldWire valueMeaning
8BeginStringFIX.4.4
9BodyLength117
35MsgTypeDOrder – Single
49SenderCompIDBOARTEAM
56TargetCompIDCOUNTERPARTY
34MsgSeqNum2
52SendingTime20240101-12:00:00.000
11ClOrdIDORD-10042
54Side1Buy
60TransactTime20240101-12:00:00.000
40OrdType1Market
388DiscretionInst0Related to displayed price
10CheckSum007
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.

Valid values

A value outside this list is not a parse error — the message still decodes — but validate() reports it as validate/value-not-in-enum.

ValueMeaningSymbolic nameDialects
0Related to displayed priceRELATED_TO_DISPLAYED_PRICE / RelatedToDisplayedPriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
1Related to market priceRELATED_TO_MARKET_PRICE / RelatedToMarketPriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
2Related to primary priceRELATED_TO_PRIMARY_PRICE / RelatedToPrimaryPriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
3Related to local primary priceRELATED_TO_LOCAL_PRIMARY_PRICE / RelatedToLocalPrimaryPriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
4Related to midpoint priceRELATED_TO_MIDPOINT_PRICE / RelatedToMidpointPriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
5Related to last trade priceRELATED_TO_LAST_TRADE_PRICE / RelatedToLastTradePriceFIX 4.4, FIX 4.2, FIX 5.0 SP2
6Related to VWAPRELATED_TO_VWAPFIX 4.4, FIX 5.0 SP2
7Average Price GuaranteeAVERAGE_PRICE_GUARANTEEFIX 5.0 SP2

Where tag 388 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.

MessageMsgTypeFIX 4.4FIX 4.2FIX 5.0 SP2Where in the message
CrossOrderCancelReplaceRequesttOptionalOptionalinside the DiscretionInstructions component
ExecutionReport8OptionalOptionalOptionalinside the DiscretionInstructions component
MultilegOrderCancelReplaceACOptionalOptionalinside the DiscretionInstructions component
NewOrderCrosssOptionalOptionalinside the DiscretionInstructions component
NewOrderListEOptionalOptionalOptionalinside ListOrdGrp › DiscretionInstructions
NewOrderMultilegABOptionalOptionalinside the DiscretionInstructions component
NewOrderSingleDOptionalOptionalOptionalinside the DiscretionInstructions component
OrderCancelReplaceRequestGOptionalOptionalOptionalinside the DiscretionInstructions component

Wire format

A single character. Most char fields are enumerated, so the value is one of a fixed set rather than arbitrary text. @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 388 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 discretionInst = message.fields[388]?.raw;// e.g. "0" — Related to displayed price// The dictionary also carries the labels:const label = fix.dictionary  .fieldByTag(388)  ?.enumValues?.find((e) => e.value === discretionInst)  ?.description;

Other char fields

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