To fill out and send a SWIFT MT199, you complete three fields in the free-format template — a sender’s reference, an optional related reference tying the message to the underlying payment, and a narrative of up to 35 lines — format every character within the SWIFT “x” character set, run the message through your institution’s dual-authorization workflow, and release it to the SWIFT gateway, where an ACK confirms the network accepted it.1ISO 20022. SWIFT MT199 Message Format The rules are strict, but the message itself is short.
Confirm the MT199 Is the Right Message
The MT199 sits in Category 1, which covers customer payments and cheques — individual and corporate wire transfers.2SWIFT. Category 1 – Customer Payments and Cheques Message Reference Guide Use it when you need to send free text about a customer payment that no structured message type can carry: a request for missing beneficiary details on an incoming transfer, a status inquiry on a stuck payment, a compliance clarification, an error notification.1ISO 20022. SWIFT MT199 Message Format
If the underlying transaction belongs to a different category, you need a different n99. Collections and cash letters use MT499; documentary credits and guarantees use MT799.1ISO 20022. SWIFT MT199 Message Format Sending an MT199 about a Category 4 or Category 7 matter will get it rejected or ignored.
Populate the Three Fields
An MT199 has three fields. Two carry references that tie the message to a transaction, and one holds the message itself.
Field 20 — Transaction Reference Number
Field 20 is mandatory. It is the reference you assign to identify this specific MT199, defined in the specification as “the reference assigned by the Sender to unambiguously identify the message.”3ISO20022. MTN99 Field 20 Transaction Reference Number It accepts up to 16 characters from the SWIFT “x” character set. Most institutions generate the value from their payment-processing system, typically building in the date and a sequence number so operations can trace the message back through the log.
Field 21 — Related Reference
Field 21 links your MT199 to the transaction you are writing about. It is optional, because not every free-format message relates to a prior payment, but when you are inquiring about a specific MT103 or MT202 you should populate it with that payment’s reference number so the receiver can pull the right record.1ISO 20022. SWIFT MT199 Message Format The field accepts up to 16 characters. A wrong value here is costly: the receiving operations desk will either attach your query to the wrong payment or send it back for clarification, and either outcome loses a day or more.
Field 79 — Narrative
Field 79 is mandatory and holds the message text. It allows up to 35 lines, each line up to 50 characters.4SWIFT. Common Group Messages for Standards MT November 2021 That is roughly 1,750 characters total — enough for a complex explanation, tight enough to force discipline. Put the essentials at the top: the payment amount, value date, originator and beneficiary names, and the specific question or instruction. Every follow-up round costs at least another business day.
Character Set and Line Breaks
All three fields use the SWIFT “x” character set. The permitted characters are the letters A–Z and a–z, the digits 0–9, and this limited set of punctuation and symbols: forward slash, hyphen, question mark, colon, parentheses, period, comma, apostrophe, plus sign, and space. Nothing else. Curly braces, ampersands, angle brackets, and most other punctuation will trigger a rejection, even though they look harmless on screen.
Line breaks in Field 79 must use the CrLf sequence (carriage return followed by line feed). A lone carriage return, a lone line feed, or the reversed LfCr order is not valid. SWIFT terminal software usually handles this for you, but if your institution composes messages through an API or middleware layer, verify the line-break encoding before you go live. A malformed break is one of the more common reasons a message that looks correct on screen comes back as a NACK.
Authorize and Transmit
Once the fields are complete, the message enters your institution’s authorization workflow before it reaches the SWIFT network. Most banks apply dual authorization, sometimes called the four-eyes principle: a second officer reviews the message for accuracy, confirms the references match the underlying payment, and checks the narrative does not disclose restricted information.5SWIFT. SWIFT Compatible Application – SWIFT gpi for Financial Institutions Label Criteria 2023 Only after that second approval does the system release the message to the SWIFT gateway.
Watch for the acknowledgment after transmission. An ACK means the SWIFT network accepted the message as valid and queued it for the receiver. It does not mean the receiver has read or acted on it. A NACK means the message failed validation, usually for a formatting error, an invalid character, or a field-length problem. The NACK carries an error code in Field 405 that identifies what went wrong, so you can correct and retransmit.
Response times vary. Routine payment inquiries generally draw a reply within one or two business days. Compliance queries can take longer; if the receiving bank’s compliance team needs to pull documentation or escalate internally, a week or more is not unusual. Sending a second MT199 that references the same Field 21 value is standard practice when a response is overdue.
Keep the Record
MT199 messages fall under the recordkeeping rules that apply to other payment-related communications. Under the Bank Secrecy Act, banks must retain records associated with funds transfers of $3,000 or more for at least five years.6FFIEC BSA/AML InfoBase. Assessing Compliance with BSA Regulatory Requirements: Funds Transfers Recordkeeping Because an MT199 is almost always attached to a payment at or above that threshold, the message and its narrative are part of the transaction record. Records can be kept as originals, microfilm, electronic copies, or reproductions, as long as they remain accessible within a reasonable period, and the U.S. Treasury Department or a law enforcement investigation can extend the retention period beyond five years on a case-by-case basis.7FFIEC BSA/AML InfoBase. Appendix P – BSA Record Retention Requirements
Plan for the ISO 20022 Switch
The SWIFT network is partway through a migration from legacy MT messages to the ISO 20022 MX format. The cross-border coexistence period for core payment instructions like MT103 and MT202 ended on 22 November 2025.8Swift. ISO 20022 for Financial Institutions Free-format messages are on a slower timeline. The MT199 is currently classified as deprecated but supported, meaning it still works on the FIN network but is no longer being updated with new business fields.9Swift. ISO 20022: Standards
For the MT199’s investigation role, the ISO 20022 replacements are camt.110 (Investigation Request) and camt.111 (Investigation Response). By November 2027, MT messages for exceptions and investigations will be phased out, and in-flow translation from ISO 20022 back to MT199 will end.10Swift. ISO 20022: Exceptions and Investigations Free-format n99 messages will remain technically available on FIN after that date, but SWIFT’s guidance is that they should no longer be used for exceptions and investigations.
The practical consequence is that the open-text narrative you compose in Field 79 today will have to be broken out into structured data elements once camt.110 takes over. If you are still sending MT199 inquiries as part of a regular workflow, a migration plan before November 2027 is on the critical path.