Lesson 08 · 6 min

Formats on the Wire

FpML, ISO 20022, and why the format a report travels in depends on the regime, not the trade.

The meaning, then the message

The last lesson ended with a report and one way of writing it down: ISO 20022 XML, its tags compressed to FinInstrmRptgTxRpt and ExctgPty. That XML is a wire format, the concrete syntax a report travels in. The report's meaning is the CDM object you built it from; the wire format is how that meaning gets spelled out to cross the wire to a repository. Two formats matter in this market, and which one a firm sends depends on the regime, not on the trade.

Start with the incumbent. FpML, Financial products Markup Language, is an XML language for OTC derivatives. A small group wrote the first version in 1999; ISDA has stewarded it since 2001, the same ISDA that stewards the CDM you have spent this course reading. For two decades FpML has carried trade confirmations, dealer-to-dealer messaging, and a great deal of regulatory reporting. The CDM did not arrive from nowhere: it builds on that FpML lineage and makes it more prescriptive, pinning down how each field is meant to be read where FpML left room.

ISO 20022, and a line that moves

The newer arrival is ISO 20022, a general standard for financial messaging, used first across payments and securities and now reaching derivatives reporting. Its data dictionary is what shortens the tag names you just saw. And here the picture splits by jurisdiction, which is worth getting exactly right rather than rounding off.

In the EU and the UK, ISO 20022 XML is mandatory for sending a report to a trade repository, and has been since the EMIR Refit: the EU switched on 29 April 2024, the UK on 30 September 2024. The same change widened the report from 129 fields to 203 in the EU and 204 in the UK, and firms that had been reporting in FpML or CSV had to migrate to the new format to keep filing.

In the United States, the CFTC has mandated no XML format at all. Swap data repositories still take FpML, CSV, and other formats, and ISO 20022 shows up in the technical specification as a reference for field values, not as a required envelope. So "FpML now, ISO 20022 later" is true when you read it as a map rather than a calendar: ISO 20022 is already the rule in Europe and the likely destination elsewhere, while FpML stays entrenched, in the US and across the whole trade-processing chain that runs before a report is ever built.

Key ideas

A format is a syntax, not a meaning
The five facts a report answers, who traded, which trade, what product, how much, and when, can be written as FpML or as ISO 20022. The report does not change; only the spelling does.
ISDA stewards both ends
FpML since 2001, the CDM today. The CDM is the more prescriptive successor: it fixes the interpretation FpML left open, which is exactly what a shared reporting rule needs to stand on.
The mandate is regional
ISO 20022 XML is required under the EU and UK Refit; the CFTC requires no particular XML. One trade caught by both regimes can owe an ISO 20022 message to one repository and an FpML or CSV file to another, for the same economics.
Migration becomes a renderer swap
When the EU moved off FpML to ISO 20022 for the Refit, firms with hand-built FpML reporting had to rebuild. A firm holding the report as a CDM object changes only the last step: same derivation, a different projection. The painful format switch shrinks to a renderer.

The same fact, two spellings

Put the two side by side on one identifier, the UTI, and the difference is exactly that: spelling.

</> the same UTI and LEI, two envelopes (illustrative)

<!-- FpML: tag names spelled out --><partyTradeIdentifier>  <issuer>W22LROWP2IHZNBB6K528</issuer>FpML spells it out  <tradeId>…K528RT4K7Q20PXM3</tradeId></partyTradeIdentifier> <!-- ISO 20022: same values, dictionary-abbreviated tags --><New>  <TxId>…K528RT4K7Q20PXM3</TxId>ISO 20022 compresses it, via its dictionary  <ExctgPty>W22LROWP2IHZNBB6K528</ExctgPty></New>

Same UTI, same LEI, two envelopes. FpML names its tags in full; ISO 20022 runs them through its dictionary, the abbreviation you met a moment ago. Neither is the meaning. The meaning is the CDM object both are printed from, which is why format stops being something firms argue about.

Try itOpen Document and walk to FinInstrmRptgTxRpt, the path from the last lesson. Those abbreviated names are ISO 20022's dictionary, modeled in cdm.regulation as ordinary types. FpML stays a separate standard outside the model. Either way the CDM sits one level up: read the model, then render to whichever envelope the regime takes.

◆ Checkpoint

01Which wire format does the EMIR Refit require for sending reports to a trade repository?

1 / 3