FIX Data Types

Read FIX wire values with formats and examples for timestamps, dates, text, numbers, prices, quantities, and repeating-group counts.

This reference applies to the FIX APIs. Type names match the downloadable dictionaries. A type describes a value’s encoding; each message’s field table defines the declared values and additional requirements.

Numbers are written as decimal text, with . as the decimal point.

Examples show individual fields or values, not complete messages. The annotated form TagName(tag)=ValueName(raw value) identifies an enum; only the numeric tag and raw value travel on the wire. For example, Side(54)=BUY(1) is sent as 54=1.

AMT

A decimal monetary amount. Example value: 0.15.

BOOLEAN

Y means yes; N means no. Example: AggregatedBook(266)=Y.

CHAR

One case-sensitive character. Example: Side(54)=BUY(1).

CURRENCY

A three-letter ISO 4217 currency code. Example value: USD.

INT

A whole number, optionally negative. Example value: 30.

LENGTH

A byte count. Example value: 128.

MULTIPLECHARVALUE

One or more characters separated by spaces. Example: ExecInst(18)=PARTICIPATE_DONT_INITIATE(6). The order placement field table lists the supported instructions.

NUMINGROUP

The number of entries in a repeating group. Example: NoRelatedSym(146)=2 announces two instrument entries; the message layout defines each entry’s fields and wire order. See Empty Groups for zero and omitted counters.

PRICE

A decimal price. Example: Price(44)=0.54. See Markets and Trading for units and price increments.

QTY

A decimal quantity. Examples: OrderQty(38)=100 and CashOrderQty(152)=54.00. The field determines whether the quantity is contracts or a notional budget.

SEQNUM

A positive message sequence number. Example: MsgSeqNum(34)=42. A field can define a special zero value, such as EndSeqNo(16)=0 for an open-ended resend range.

STRING

Case-sensitive text. Example: ClOrdID(11)=client-order-1.

UTCDATEONLY

A UTC calendar date in YYYYMMDD form. Example value: 20261029.

UTCTIMEONLY

A UTC time in HH:MM:SS form, optionally followed by fractional seconds. Example value with milliseconds: 18:10:45.123.

UTCTIMESTAMP

A UTC date and time. The exchange writes timestamps as YYYYMMDD-HH:MM:SS.sss, with three fractional digits for milliseconds:

ValidUntilTime(62)=20270115-08:00:00.000

This means January 15, 2027 at 08:00:00.000 UTC. The date has no separators, a hyphen joins the date and time, and UTC is implicit: there is no T, Z, or numeric offset. This differs from the RFC 3339 timestamps used by REST and WebSocket.

The standard type definitions are specified in the FIX Trading Community’s FIX protocol data types, section 5. FIX Protocol specification copyright FIX Protocol Limited.