MT599 Free Format Message (Securities)

When MT599 is used

The MT599 belongs to the common group of free format messages, the MTn99: the same layout exists in most categories, and the category digit routes the message to the right team at the receiver. A 5 sends it to the securities operations or custody team, where an MT199 goes to customer payments and an MT999 to cash management. Choose MT599 when the subject is a securities trade, holding, account or corporate action.

Typical MT599 traffic: a client asks its custodian why a dividend or coupon has not been credited, quoting the corporate action reference; a custodian asks for missing tax documents or beneficial owner details; a broker asks a counterparty to cancel and re-instruct an unmatched trade; a CSD or custodian announces a change to its deadlines or services; a client tells its servicer about a change to its own Swift setup. Some market infrastructures name the MT599 as the channel for specific notices, with an "ATTENTION OF" line naming the team.

The MT599 is not an instruction channel. Settlement instructions (MT540 to MT543), corporate action elections (MT565), cancellations and transaction processing commands have their own messages, which are validated, matched and processed automatically. An instruction sent as free text bypasses all of that: it is handled manually, if at all, it may miss a market deadline, and it cannot be matched or reported on in the normal way. Check your custodian’s service terms to see whether it accepts any instruction by free format. If an MT599 seems to ask you to move securities or cash, confirm it through the structured message or a known channel before acting.

Free text also carries an operational and fraud risk: there is no field-level validation, so a wrong ISIN, account or amount is not caught, and a convincing message that asks for a change of standing settlement instructions or a payment to a new account is a classic social engineering route. Treat change requests received by MT599 like any other unverified request.

For queries about a specific instruction, the category 5 queries and answers (MTn95 and MTn96) or a request for cancellation (MTn92) are alternatives where both sides support them. The n99 format does not apply in categories 4 and 7, which have their own free format messages (MT499 and MT799).

MT599 format: sequences and fields

Rules worth knowing

• Use an MT599 only for information for which no other message type exists. A structured message, where one exists, is the only one the receiver processes automatically.
• Field 79 holds at most 35 lines of 50 characters in the Swift x character set. Characters outside the set, such as @, & or accented letters, are not allowed.
• Fields 20 and 21 must not start or end with a slash or contain "//".
• Choose the category digit that routes the message to the unit that can act on it. Use MT599 for securities, not MT199 or MT999.
• An MT599 is not a valid way to give a settlement instruction, a cancellation or a corporate action election unless your agreement with the receiver says so.

MT599 example

ZagTrader Test Bank (ZAGTAEADXXX) holds 40,000 shares of a test security with its custodian CUSTGB2LXXX. The cash dividend announced for payment on 22 October 2026 has not been credited, and no MT566 has arrived. ZagTrader queries the custodian, quoting the corporate action reference from the MT564.

{1:F01ZAGTAEADAXXX0000000000}{2:I599CUSTGB2LXXXXN}{4:
:20:ZT599-261023-01
:21:DVCA2610ZAG01
:79:ATTN CORPORATE ACTIONS - INCOME
ACCOUNT ZAG-SAFE-0001
ISIN GB00ZAGT0013 CASH DIVIDEND DVCA
PAY DATE 20261022 ELIGIBLE 40000 UNITS
NO CREDIT AND NO MT566 RECEIVED TO DATE.
PLEASE CONFIRM PAYMENT STATUS AND
EXPECTED VALUE DATE.
-}

Line by line

The custodian would answer with its own MT599 quoting ZT599-261023-01 in field 21, or simply send the MT566 once the dividend is paid.

All BICs, references and accounts are made up; the ISIN has a valid check digit.

Common errors and rejects

1. Line in field 79 longer than 50 characters

   Each line holds at most 50 characters and the field at most 35 lines. Text pasted from e-mail or a ticketing tool often has long lines and fails format validation. Wrap it before sending.

2. Characters outside the Swift x set

   Characters such as @, &, accented letters or curly quotes are not in the x character set. They fail validation or are replaced on the way, which can make an e-mail address or a name unreadable. Spell them out.

3. Instruction sent as free text was not executed

   A settlement instruction, cancellation or corporate action election sent by MT599 is not processed by the custodian’s automated flow. It may be ignored or handled too late for the market deadline. Send the structured message (MT540 to MT543, MT565) and use MT599 only to explain it.

4. Query cannot be tied to a transaction

   Without field 21 and the key details in the first lines (account, ISIN, reference, date), the receiving team has to search for the subject, and answers take days. Quote the reference the receiver knows, such as its SEME, CORP or MITI.

5. Sent in the wrong category

   An MT199 or MT999 about a securities matter is routed to a payments or cash team at the receiver and may sit unread. Use MT599 for securities subjects.

ISO 20022

There is no ISO 20022 equivalent of the MT599: Swift’s MT and MX equivalence table lists none. Free text about payments moves to structured case management messages such as camt.056 and camt.029, but nothing replaces the MT599 for securities.

Securities messages were not part of the November 2025 payments deadline, and the MT599 remains in use on FIN.

Related messages

• MTn99Free Format Message
• MT199Free Format Message
• MT299Free Format Message
• MT999Free Format Message
• MT799Free Format Message
• MTn95Queries
• MTn96Answers
• MTn92Request for Cancellation
• MT540Receive Free
• MT543Deliver Against Payment
• MT564Corporate Action Notification
• MT565Corporate Action Instruction
• MT566Corporate Action Confirmation

MT599 questions

What is an MT599 message used for?

For securities-related information for which no structured message exists: queries to a custodian or broker, requests for documents, explanations of a problem with a trade or corporate action, and notices about services or deadlines.

Can I send a settlement instruction by MT599?

You should not. Settlement instructions have their own messages (MT540 to MT543) that are validated, matched and processed automatically. An instruction by MT599 is handled manually, if at all, and your custodian may not accept it.

What is the difference between MT599, MT199 and MT999?

They have the same layout (fields 20, 21 and 79). The category digit decides where the message goes at the receiver: MT199 to customer payments, MT599 to securities, MT999 to cash management. See the MTn99 page for the whole group.

How long can an MT599 be?

Field 79 holds up to 35 lines of 50 characters, so about 1,750 characters of text. Longer content has to be split over several messages, each quoting the first one in field 21.

Is there an ISO 20022 version of the MT599?

No. Swift’s MT and MX equivalence table lists no ISO 20022 equivalent for the MT599.