RegistID

FIX Field 513

Tag	Name	Type	Enumerated	First introduced
513	RegistID	String		FIX.4.3

Unique identifier of the registration details as assigned by institution or intermediary.

Notes

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Links from FIXwiki pages to relevant discussions on the FPL site are very valuable.

For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
following relevant link, http://www.fixprotocol.org/discuss/read/f5014573, to back up your points.