Returns

The return family: MT103 and MT202 returns (the /RETN/ codeword in :72:) to and from pacs.004, with reason codes, original references and charges.

Formats

Format	What it is	Versions accepted	Emitted by default
`mt103-retn`	MT103 carrying `/RETN/` in `:72:` (customer transfer returned)	n/a	n/a
`mt202-retn`	MT202 carrying `/RETN/` in `:72:` (bank transfer returned)	n/a	n/a
`pacs.004`	Payment return	`.001.09` – `.001.13`	`.001.09`

Pairs

From	To
`mt103-retn`, `mt202-retn`	`pacs.004`
`pacs.004`	`mt103-retn`, `mt202-retn`

A return is never a new payment and never a reject: mt103-retn → pacs.008 and mt103-retn → pacs.002 do not exist. There is no canonical source for this family.

How fields map

The canonical model is a payment return: who pays the money back, how much, why, and which original payment it answers.

MT to pacs.004.

:20: becomes the message id and the return id.
:32A: becomes the settlement date and the returned amount; MT103 :33B: becomes the original amount.
The block 3 UETR {121:} becomes the original UETR: a return travels under the UETR of the payment it returns.
:52a: becomes the institution paying back (return chain debtor); MT103 :57a: or MT202 :58a: the institution being paid (return chain creditor); :56a: the intermediary.
MT202 :21: becomes the original end-to-end id.
MT103 :71F:/:71G: become charges.
:72: is read line by line through the codeword table below.

`:72:` line	Becomes
`/RETN/`	The return marker. A reason-code suffix (`/RETN/AC04`) is the reason; a field-tag suffix (`/RETN/32A`) is dropped
`/AC04/ACCOUNT CLOSED`	Reason code `AC04`, with the text as additional information
`/MREF/<ref>`	Original instruction id
`/TREF/<ref>`	Original end-to-end id (wins over MT202 `:21:`)
`/CHGS/EUR10,00`	A charge
`/TEXT/<text>` or plain text	Additional information

pacs.004 to MT. The reverse: :72: is written as /RETN/<reason>, /MREF/, /TREF/ (MT103) and /TEXT/ lines in that order. Charges become :71F: on an MT103 and /CHGS/ lines on an MT202.

Where information is lost

Situation	Warning
Ordering customer and beneficiary of an MT103 return (the return model has no customer parties)	`DROP_FIELD`
Correspondent and other agents with no slot in the return chain	`DROP_AGENT`
A return chain with only one end known: pacs.004 needs both, so the chain is left out	`DROP_AGENT`
A charge with no levying institution (pacs.004 requires one)	`DROP_FIELD`
A reason or codeword with no table row, carried as proprietary text	`RETURN_REASON_UNMAPPED`
The same charge in `:71G:` and `/CHGS/`, collapsed to one	`CHARGES_DUPLICATED`
MT103 return: `:23B:CRED`, `:71A:SHA` and `NOTPROVIDED` customer fields written because MT103 requires them	`MISSING_REQUIRED_DEFAULTED`
pacs.004 creation time and settlement method (`INDA`)	`MISSING_REQUIRED_DEFAULTED`
`:72:` over six lines of 35; additional information over 105 characters	`TRUNC_REMITTANCE`

Conventions

Detection. transmute scans :72: for /RETN/ and routes the message to mt103-retn or mt202-retn automatically. If you send from=mt103 for a message that carries /RETN/ (or from=mt103-retn for one that does not), the request is invalid-input 400.
Reason codes pass through. Four-character ISO return reasons (AC04, AM05, MS03, CUST, …) are carried verbatim, including codes transmute has never seen. Nothing is rejected for an unknown reason.
MT202 returns need both banks. An MT202 return requires :58a:. A pacs.004 without a return chain cannot become an mt202-retn and the conversion is refused.
One file, one family. A file of several MT103 or MT202 messages that includes a /RETN/ message is rejected: send returns separately from payments.

Example

curl -sS -X POST "https://api.transmute.403fin.io/v1/convert?to=pacs.004" \
  -H "Authorization: Bearer $TRANSMUTE_KEY" \
  -H "Content-Type: text/plain" \
  --data-binary @- <<'MT'
:20:RTN-103-0100
:23B:CRED
:32A:260610EUR985,50
:33B:EUR1000,00
:50K:/DE89370400440532013000
JANE EXAMPLE
:57A:AAAADEFF
:59:/GB29NWBK60161331926819
ACME TOOLS LTD
:71A:SHA
:72:/RETN/32A
/AC04/ACCOUNT CLOSED
/MREF/INSTR-0001
/TREF/E2E-2026-0001
MT

The result document, formatted:

<TxInf>
  <RtrId>RTN-103-0100</RtrId>
  <OrgnlInstrId>INSTR-0001</OrgnlInstrId>
  <OrgnlEndToEndId>E2E-2026-0001</OrgnlEndToEndId>
  <OrgnlIntrBkSttlmAmt Ccy="EUR">1000.00</OrgnlIntrBkSttlmAmt>
  <RtrdIntrBkSttlmAmt Ccy="EUR">985.50</RtrdIntrBkSttlmAmt>
  <IntrBkSttlmDt>2026-06-10</IntrBkSttlmDt>
  <RtrRsnInf><Rsn><Cd>AC04</Cd></Rsn><AddtlInf>ACCOUNT CLOSED</AddtlInf></RtrRsnInf>
</TxInf>

"warnings": [
  { "code": "MISSING_REQUIRED_DEFAULTED", "severity": "info", "targetField": "GrpHdr/CreDtTm", "detail": "..." },
  { "code": "MISSING_REQUIRED_DEFAULTED", "severity": "info", "targetField": "GrpHdr/SttlmInf/SttlmMtd", "detail": "..." },
  { "code": "DROP_FIELD", "severity": "info", "sourceField": ":23B:", "detail": "..." },
  { "code": "DROP_FIELD", "severity": "lossy", "sourceField": ":50a:", "detail": "..." },
  { "code": "DROP_FIELD", "severity": "lossy", "sourceField": ":59a:", "detail": "..." },
  { "code": "DROP_FIELD", "severity": "info", "sourceField": ":71A:", "detail": "..." },
  { "code": "DROP_FIELD", "severity": "info", "sourceField": ":72:", "detail": "..." },
  { "code": "DROP_AGENT", "severity": "lossy", "sourceField": "creditorAgent", "targetField": "TxInf/RtrChain/Cdtr", "detail": "..." }
],
"meta": { "detectedType": "mt103-retn", "targetType": "pacs.004.001.09", "...": "..." }

The customer parties and the 32A pointer are dropped, and because the message names only the creditor-side bank (:57A:), the one-legged return chain is left out rather than half-written.

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