From FIXwiki

FIX Message Component Parties

The Parties component block is used to identify and convey information on the entities both central and peripheral to the financial transaction represented by the FIX message containing the Parties Block. The Parties block allows many different types of entites to be expressed through use of the PartyRole field and identifies the source of the PartyID through the the PartyIDSource.

See "Volume 6 - APPENDIX 6-G - USE OF PARTIES COMPONENT BLOCK" for additional usage information..

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Notes

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For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
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