Explained to kids!
A MID is a number that says which shop was paid. A TID is a number that says which till in that shop took the payment. With these two numbers, the bank always knows where the money must go.
Let’s see it in real life…
Mei is 8. She lives with her parents and her grandmother, Nai Nai.
On Sundays, the family sells dumplings and tea at the big covered market.
The market office gave the stall a number: stall 27. It is painted on a small sign.
The stall has two cash boxes. Box 1 is for dumplings. Box 2 is for tea.
Every ticket Mei hands out says "Stall 27, Box 1" or "Stall 27, Box 2".
Many customers pay with market tokens, which the office changes into money at night.
In the evening, the office counts the tokens from each stall and sends the money to the right family.
One Sunday, the dumpling money looks too small. Nai Nai checks the tickets from Box 1.
She finds the mistake fast: some dumpling tickets were written at Box 2.
On the office’s list, stall 27 also has a word next to it: "food". It tells what the stall sells.
That is a MID and a TID.
Tiny recap
- It means… one number for the shop (MID) and one number for each till or machine (TID).
- It helps when… money from many shops is mixed together and must go back to the right one.
- Watch out for… using the wrong till or the wrong number. The money can end up in the wrong place.
…detailed for specialists
MID and TID are the two identifiers that locate a card payment. The merchant ID (MID) is the number an acquirer assigns to a merchant account, used to route funds, fees and disputes. The terminal ID (TID) identifies the specific point of acceptance under that MID, such as a card terminal, a till or an online checkout.
For PSPs, PayFacs and platforms, these identifiers are the backbone of operations in 2026. Multi-acquiring, omnichannel selling and marketplace models multiply accounts and devices. Each new acquirer, country, brand or store adds identifiers that must be created, mapped and reconciled. An operator that models them well can onboard and report cleanly. One that does not spends its time explaining payouts.
What are a MID and a TID?
A MID identifies who is paid, and a TID identifies where the payment was taken. Both are set by the acquirer or processor, not by the card schemes, and both travel in every authorization and clearing message.
The international message standard for card transactions, ISO 8583, whose third edition was published in July 2023, defines the relevant data elements. The card acceptor identification code, which carries the MID, has 15 characters. The card acceptor terminal identification, which carries the TID, has 8 characters. The same standard carries the merchant type as a four-digit code and the card acceptor name and location in a 40-character field.
In practice, a MID is created when a merchant account is opened and stays with it for its whole life. It is printed on receipts, quoted in support calls and used as the key in acquirer statements. A TID is created each time a device or a channel is added. On a card receipt, both usually appear near the top, next to the merchant’s name and address.
There is no global MID registry. A merchant with three acquirers has at least three MIDs, in three formats. Schemes, acquirers and processors also use their own internal identifiers on top.
Related notions:
- MCC: the merchant category code, a four-digit number that classifies the merchant’s business. See our episode on the merchant category code.
- ISO 18245: the ISO standard that defines merchant category codes.
- Merchant descriptor: the name and location shown on the cardholder’s statement.
- Sub-merchant ID: the identifier a payment facilitator assigns to each merchant it sponsors.
- Payment facilitator ID: the identifier a scheme assigns to the facilitator itself.
- Acquirer BIN or ICA: the identifier of the acquirer in Visa’s and Mastercard’s systems.
MID vs TID vs MCC: how do the identifiers compare?
The three identifiers answer three questions: who, where and what. The list below sets them side by side.
- MID: identifies the merchant account. Assigned by the acquirer. Up to 15 characters in ISO 8583. Drives settlement, pricing, disputes and monitoring.
- TID: identifies the terminal or channel. Assigned by the acquirer or processor. 8 characters in ISO 8583. Drives device management, batch closing and store-level reporting.
- MCC: identifies the type of business. Chosen by the acquirer from the scheme lists. Four digits. Drives interchange, risk rules, authorization behavior and rewards.
- Descriptor: identifies the merchant to the cardholder. Set by the merchant with its acquirer. Visa limits the merchant name to 25 characters in its messages.
- Sub-merchant ID: identifies a sponsored merchant under a payment facilitator’s own MID structure.
Two further points are often misunderstood. First, an online checkout has a TID even though no device exists, because the gateway connection to the acquirer needs one. Large merchants may use several virtual TIDs to separate websites, apps or call centers. Second, the identifiers that the merchant sees are not always those the schemes see. Acquirers and processors keep internal numbers and translate them, which is one reason why a dispute file and a settlement file may refer to the same merchant in two ways.
The hierarchy is simple: one merchant can hold several MIDs, each MID carries one MCC, and each MID has one or more TIDs.
How do a MID and a TID work in a transaction?
The identifiers are set once at onboarding and then included in every message. The steps, from the merchant to the issuer and back, are:
- Underwriting. The acquirer, or the PSP or payment facilitator acting for it, reviews the merchant and decides which accounts are needed.
- MID creation. The acquirer creates the MID, with its MCC, currency, pricing and settlement account. Visa’s Merchant Data Standards Manual, dated October 2026, requires acquirers to select the MCC that most accurately describes the merchant’s business.
- TID creation. The acquirer or processor creates one TID per terminal, till or online channel and loads it into the device or gateway.
- Authorization. At each payment, the terminal or gateway sends the MID, TID, MCC and descriptor with the card data. The acquirer forwards the request through the scheme to the issuer.
- Issuer decision. The issuer uses the MCC and merchant data in its risk and authorization rules.
- Batch. At the end of the day, each TID closes its batch and the acquirer submits the transactions for clearing.
- Settlement. The acquirer settles funds per MID to the linked bank account, net of fees, as explained in settlement and payout.
- Reporting. Statements, disputes and scheme monitoring are organized per MID. Store and device reports are organized per TID.
MIDs and TIDs in numbers (2026)
The identifiers follow fixed formats, and the networks they describe are very large. Key figures:
- 15 and 8 characters: maximum lengths of the card acceptor identification code and of the terminal identification in ISO 8583.
- 4 digits: length of an MCC. Mastercard’s Quick Reference Booklet of April 2024 lists codes from 0742 to 9406, with ranges reserved for airlines, car rental and lodging.
- February 2023: publication of the second edition of ISO 18245, the standard for merchant category codes.
- 175 million: merchant locations accepting Visa as of June 30, 2025, according to Visa’s fact sheet.
- 64 million: estimated number of those locations reached through payment facilitators, in the same document. More than a third of locations are sub-merchants.
What are the risks and limits of MIDs and TIDs?
The identifiers are simple, and most problems come from how they are assigned and maintained.
- Wrong MCC. A code that does not reflect the real business leads to wrong interchange, unexpected declines and scheme compliance issues. It is also treated as a rule violation.
- One MID for several businesses. Mixing activities under one MID hides each activity’s dispute and fraud ratios. Visa’s manual says a merchant with more than one line of business must use the MCC of its main business or different MCCs for each line.
- MID proliferation. One MID per acquirer, currency, brand and country quickly becomes hundreds. Without a clear model, reconciliation and reporting break.
- Shared or cloned TIDs. Two devices using the same TID corrupt batches and make refunds and disputes hard to trace.
- Opaque descriptors. A statement name the cardholder does not recognize causes disputes.
- Aggregation. A facilitator that sends transactions without proper sub-merchant identifiers breaches scheme rules. Visa’s Payment Facilitator and Marketplace Risk Guide requires facilitators to assign a unique identifier to each sponsored merchant and to include it in all transactions.
- Uses beyond payments. MCCs are used outside the card system. In the US, the IRS allows payers to rely on the MCC to decide whether card payments are reportable, under Revenue Procedure 2004-43. A wrong code has tax consequences for the merchant’s customers.
- Local schemes. Domestic card schemes add their own identifiers. In France, covered in our guide to payment methods in France, the domestic scheme uses its own merchant contract number next to the international MIDs.
MIDs and TIDs: what changes for PSPs, PayFacs and platforms
Operators create, store and translate these identifiers for their merchants. Five areas need a clear design.
Onboarding and account structure
The account structure should be decided before the first MID is requested: one per legal entity, per country, per brand or per business line. The article on multi-acquirer merchant onboarding shows how one application can feed several acquirers. Payment stack activation covers the step where acquirer accounts and credentials are attached to a merchant.
PayFac and ISO models
In an ISO model, each merchant gets its own MID from the acquirer. In a PayFac model, the facilitator works under its own registration and identifies each sub-merchant with a sub-merchant ID, name, MCC and address. Adyen’s documentation for payment facilitators lists these fields for Visa, Mastercard and American Express. The differences are explained in PayFac vs ISO.
Routing across acquirers
With multi-acquiring, a single merchant has one MID per acquirer, and the routing engine chooses among them for each payment. The operator needs an internal merchant reference above the acquirer MIDs, so that reports, refunds and disputes follow the merchant, not the acquirer.
In-store estates
Every terminal has a TID, and terminals move, break and get replaced. A terminal inventory linked to stores and tills is the basis of store-level reporting. The in-store payments Matcher page describes how in-store transactions are matched to orders, and the article on how Matcher simplifies POS transaction reconciliation gives the context.
Data quality over time
Identifiers decay. Stores close, terminals are swapped, merchants add a brand or change their activity. A yearly review of each merchant’s MIDs, MCCs, descriptors and active TIDs prevents most surprises. Changes should be logged with dates, since a dispute can refer to a transaction made months earlier under an identifier that no longer exists.
Multi-brand and multi-entity groups
Groups that run several brands or legal entities need separate MIDs for settlement and a consolidated view for management. Multi-brand operations depend on this mapping. The Payments Library study Payments from a merchant’s perspective: a European assessment gives the merchant’s side of these costs, and the #TheShot episode Why merchants connect directly to card schemes discusses what changes when a large merchant gets closer to the networks.
Is a clean MID and TID structure worth the effort in 2026?
Yes. The identifiers look like plumbing, and every operational question depends on them: where a payout went, which store took a payment, which business line has a dispute problem, which acquirer charged which fee. A clean structure costs time at onboarding and saves it every day afterwards. The effort grows with the business: a single shop needs one MID and a few TIDs, while a platform with thousands of sub-merchants and several acquirers needs a proper data model, naming rules and automated checks. What it means by player:
- PSPs: keep one internal merchant reference and map every acquirer MID and TID to it.
- PayFacs: assign stable sub-merchant IDs, send them in every transaction, and choose each sub-merchant’s MCC with care.
- ISOs: document which MID and TID belong to which location and device, and update the record when terminals are swapped.
- ISVs and platforms: store the identifiers with each transaction, so that software reports and bank statements can be compared line by line.
A MID says who is paid, a TID says where the payment was taken, and operators who keep both in order can always explain where the money went.
Frequently Asked Questions
What is a merchant ID (MID)?
A merchant ID (MID) is the unique number an acquirer assigns to a merchant account. It identifies the merchant in every card transaction and tells the acquirer where to settle funds, which fees to apply and where to send disputes. A MID is specific to one acquirer, so a merchant with several acquirers has several MIDs.
What is the difference between a MID and a TID?
A MID identifies the merchant account, and a TID identifies a specific terminal or point of acceptance under that account. The MID tells the acquirer who must be paid. The TID tells which device, till or online checkout took the payment. One MID usually has several TIDs, and both are sent in every card transaction.
Can one merchant have several MIDs?
Yes. One merchant can have several MIDs, and many do. A separate MID is common for each acquirer, country, currency, legal entity or brand, and for each distinct line of business with its own merchant category code. Several MIDs make pricing and risk clearer, but they add work in reconciliation and reporting.
How is the MCC linked to a MID?
The MCC is assigned to a MID by the acquirer when the merchant account is created. Each MID carries one merchant category code, which describes the merchant’s main business. The code is then sent with every transaction from that MID. It influences interchange, issuer risk rules and scheme requirements.
What is ISO 18245?
ISO 18245 is the international standard titled "Retail financial services: Merchant category codes". It defines code values used to group merchants by type of business, trade or service. Its second edition was published in February 2023. Card schemes publish their own MCC lists based on the same four-digit structure.
