Usage of User-defined Tags

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Imported from previous forum

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The fix protocol supports user-defined tags and messages.

Are user-defined tags only allowed within user-defined messages or is it also allowed to add them to a standard message ?

I can’t find an explicit statement in the documentation that forbids/allows this.

Thanks for your help

Frank Eiberle

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[ original email was from Ryan Pierce - rpierce@taltrade.com ]
> The fix protocol supports user-defined tags and messages.
>
> Are user-defined tags only allowed within user-defined messages or is it also allowed to add them to a standard message ?
>
> I can’t find an explicit statement in the documentation that forbids/allows this.

User-defined tags may be used in standard messages. If you need to send an order with a user-defined tag, it would be much better to add the tag to the order message, rather than create a user-defined message including all of the order’s tags plus the user-defined tag.

You can’t expect counterparties to understand or send specific user-defined tags without bilateral agreement. You should register your user-defined tags on the fixprotocol.org web site; doing so reserves the tag number, and if everyone registers their tags, duplication of tag numbers for different purposes becomes unlikely. Tags that may be used in a scope extending beyond one firm and its trading partners should be brought to a working group, or the Tech Committee, as candidates for inclusion in the next spec version.

4

[ original email was from Tayloe Draughon - tayloed@capital-mkts.com ]
> The fix protocol supports user-defined tags and messages.
>
> Are user-defined tags only allowed within user-defined messages or is it also allowed to add them to a standard message ?
>
> I can’t find an explicit statement in the documentation that forbids/allows this.
>
> Thanks for your help
>
> Frank Eiberle
>

Yes you can use user defined tags in any message.

It is a good idea to check newer versions of FIX to see if your user defined tag has been already been defined as a standard tag. If so, you might want to consider using the new tag instead. It is also a good idea to ask to see if there is a tag, or tag combinations that might meet your functional needs.

When defining user defined tags it is best if you can go to the extent of defining the domain of expected values and data type.