ISO 8583 MTI Codes: The Complete List

How to read an MTI: four digits, four questions

Take 0420 apart left to right: 0 = ISO 8583:1987, 4 = reversal class, 2 = advice, 0 = sent by the acquirer. Read that way, "reversal advice from the acquirer, 1987 dialect" falls straight out of the digits — no table lookup needed once the four positions are second nature. Here is each position in full.

Digit 1 — version

Digit 2 — message class

Digit 3 — function

This digit carries the most operational weight: a request can be declined, an advice cannot. Whether you send x400 or x420 is not a stylistic choice — see 0400 vs 0420 below.

Digit 4 — origin

The full MTI table

Every MTI below links to its own anchor (#m0100, #m0420, …), and the names match this site's parser and MTI decoder. Responses answer on the same class: a 0100 is answered by a 0110, never by a 0200.

Authorization — 01xx

Dual-message systems authorize now and move money later, in clearing. These MTIs only ever place or report a hold. A complete 0100/0110 pair, field by field, is in the worked message examples.

Financial — 02xx

Single-message systems: authorization and posting in one step, typical of ATM, PIN debit and many domestic networks. A worked 0200/0210 ATM withdrawal is in the message examples.

File actions — 03xx

Maintaining files on the other side of the link: hot-card and negative files, parameter tables, batch record uploads.

Reversals and chargebacks — 04xx

Undoing what a previous message did. A 0400 with DE90 pointing at its original is walked through in the message examples; the full failure-path story — timeouts, repeats, orphaned holds — is in Reversals, timeouts & repeats. Note that in the major card schemes chargebacks travel in clearing files, not in online 04xx messages — online, this class is almost always reversals.

Reconciliation — 05xx

Cutover totals: counts and amounts for the day or session, exchanged so both sides can settle against the same numbers.

Administrative — 06xx

Messages that move no money and manage no link: free-text messages between institutions, administrative queries, and scheme-specific uses.

Fee collection — 07xx

Fees charged between institutions. In the international schemes these mostly travel in clearing files rather than on authorization links, so 07xx traffic is rare on the wire — but the grid defines it, and some domestic networks use it.

Network management — 08xx

Messages about the link itself. The MTI only says "network management" — the actual operation (sign-on, sign-off, echo test, key exchange) lives in DE70. Full treatment, including a parseable echo test, in 0800 / 0810 network management messages.

The 1993 family — 1xxx

ISO 8583:1993 keeps the same grid and changes the first digit to 1, so everything above transfers: 1100 reads exactly like 0100. What 1993 adds in practice is real use of function digits 4–7 — notifications that expect no response at all. That is why Mastercard's IPM clearing format, which is built on 1993, is full of xx4x types.

0100 vs 0200: dual-message or single-message, not "pre-auth or purchase"

The most common misreading of the MTI table is that 0100 means pre-authorization and 0200 means purchase. It doesn't. The difference is which architecture the transaction travels through:

• 0100 — dual-message. The authorization travels now; the financial record follows later in clearing. An approved 0100 has moved no money — it placed a hold. Typical of credit card POS and e-commerce.
• 0200 — single-message. Authorization and the financial record travel together; an approved 0210 means the posting is done. Typical of ATM and PIN debit.

Whether a transaction is a pre-authorization is signalled in DE3 (processing code) and the POS-related fields, not in the MTI. The practical consequence of the real distinction: an approved 0100 still needs a clearing record to become money, while an approved 0200 already is money — which is also why their reversal deadlines feel so different. The full flow is in the transaction lifecycle.

0400 vs 0420: asking to reverse vs announcing a reversal

Both undo a transaction; they differ in who has already acted:

Sending the wrong one hurts: send a 0400 when you've already voided locally, and a decline leaves you stuck — you can't un-void. The advice flow exists precisely so the undo can be made durable first and communicated after. Timeout rules, repeat scheduling and DE90 matching are covered in Reversals, timeouts & repeats.

Digit 4: who sent it, and how repeats are marked

The same class-and-function pair means something different depending on the last digit. 0420 is a reversal advice from the acquirer — the everyday timeout reversal. 0422 is the same advice from the issuer, which some networks use when the issuer side backs a transaction out. And the odd values are repeats: 0401 re-sends a 0400, 0421 re-sends a 0420.

The repeat rule is strict and worth engraving: nothing but digit 4 may change. DE7 (transmission time) and DE11 (STAN) must keep their original values, because they are how the receiver deduplicates. A retry that helpfully generates a fresh STAN is not a repeat — it is a brand-new transaction, and it is how a great many double-charge incidents are born. Repeats are answered with the same response type as the first attempt: a 0401 gets a 0410, a 0421 gets a 0430.

0800 / 0810: covered in depth elsewhere

Network management deserves its own treatment because the interesting part isn't the MTI — it's DE70 (sign-on 001, sign-off 002, echo test 301, key exchange 101…), heartbeat intervals, and what happens when echoes stop coming back. All of that, plus an 0800 you can paste straight into the parser, is in 0800 / 0810 network management messages.

What this table can and cannot promise

👉 To decode an MTI interactively, use the MTI decoder; to see MTIs in full messages with every field explained, start with the worked message examples — each one opens in the parser with one click.

Read next

• Reading ISO 8583: MTI, Bitmaps & Data Elements
• The Transaction Lifecycle: Authorization → Clearing → Settlement
• Reversals, Timeouts & Repeats: The ISO 8583 Failure Paths
• 0800 / 0810 Network Management Messages