> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kraken.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Header & Trailer

> Standard FIX message header and trailer fields

<div className="api-banner">
  <span className="api-protocol fix">FIX</span>
  <span className="api-detail">session: admin</span>
  <span className="api-tag">35=\*</span>
</div>

The baseline specification for this API is FIX 4.4. A standard header must be present at the start of every message in both directions. All messages sent in either direction should contain both **SenderCompID** and **TargetCompID**.
These values will be communicated by Kraken during the onboarding process.

## Standard Header

<ResponseField name="8 - BeginString" type="string" required>
  Must be `FIX.4.4`
</ResponseField>

<ResponseField name="9 - BodyLength" type="integer" required>
  Length of message expressed as the number of characters in the message following the BodyLength field up to, and including, the delimiter immediately preceding the checksum tag (10).
</ResponseField>

<ResponseField name="35 - MsgType" type="char" required>
  The message type.
</ResponseField>

<ResponseField name="34 - MsgSeqNum" type="integer" required>
  The sequence number for this message.
</ResponseField>

<ResponseField name="52 - SendingTime" type="string" required>
  Time of message transmission by the sender expressed in UTC. Format: `YYYYMMDD-HH:MM:SS.uuu`
</ResponseField>

<ResponseField name="49 - SenderCompID" type="string" required>
  Identifies the party sending the message.
</ResponseField>

<ResponseField name="56 - TargetCompID" type="string" required>
  Identifies the party receiving the message.
</ResponseField>

<ResponseField name="122 - OrigSendingTime" type="string">
  If no data is available, this value is set to the SendingTime value. Format: `YYYYMMDD-HH:MM:SS.uuu`

  <span className="field-attr">Condition:</span> Required for retransmission of message
</ResponseField>

<ResponseField name="43 - PossDupFlag" type="boolean">
  Indicates possible retransmission of message with this sequence number.
</ResponseField>

***

## Standard Trailer

<ResponseField name="10 - Checksum" type="string" required>
  Always the last field in a FIX message.
</ResponseField>