Payment routing is the set of decisions that sends a payment instruction along a particular path: through a chosen acquirer or processor, over a chosen network or rail, and on to the bank that holds the payer's funds. Every electronic payment is routed somewhere, whether the choice is fixed in a contract, set by a rule in a switch, or made fresh for each transaction by software.
The term covers several layers. At the merchant level it means picking which processor or acquiring relationship handles a sale. At the network level it means the card scheme or debit network that carries the message. At the bank level it means the rail chosen for a transfer, such as the ACH, a wire or an instant scheme. Payment routing is related to, but broader than, smart payment routing, which is the practice of making those choices dynamically on cost, approval and uptime data.
Payment routing in plain terms
Think of sending a parcel. You decide which courier to use, the courier decides which depots and lorries carry it, and the local office delivers it to the door. The parcel gets there either way, but the price, the speed and the chance of it going missing all depend on the path.
A payment works the same way. The money does not travel as a lump; a message travels, asking each party along the way to agree and to record the transfer. Routing is choosing that path. A shop might always use one courier because that is what its contract says, or it might pick the cheapest or most reliable courier for each parcel. The person paying rarely sees any of this, but it affects whether the payment is approved and how much the shop pays to accept it.
How routing works for card payments
In a card payment the merchant's payment gateway sends the transaction to a payment processor working for the acquirer. The processor reads the Bank Identification Number (BIN), the first six or eight digits of the card number, to work out which network and which issuer the card belongs to. The network then forwards the payment authorization request to the issuing bank, which approves or declines it.
Where a card carries more than one network, routing becomes a real choice. Many US debit cards carry a global brand and a domestic PIN network, and the Durbin Amendment and the Federal Reserve's Regulation II require issuers to enable at least two unaffiliated networks so that merchants can pick one. A Regulation II amendment that took effect on 1 July 2023 made clear that this applies to card-not-present transactions too. In the EU, Article 8 of the Interchange Fee Regulation (Regulation (EU) 2015/751) lets merchants install automatic brand selection on co-badged cards, while letting the cardholder override it. These rules underpin debit routing and least cost routing.
Routing for bank transfers and cross-border payments
For account-to-account payments, routing starts with the bank identifiers. In the US the nine-digit routing number tells the sending bank where to deliver an ACH or wire payment; in Europe the IBAN and BIC do the same job, and the UK uses sort codes. The sending bank then picks a rail by amount, urgency and cost: a low-value batch on ACH, a large urgent transfer on Fedwire, or an instant payment on a scheme such as SEPA Instant Credit Transfer or Faster Payments.
Cross-border routing adds more choices. A bank may send a SWIFT MT103 or its ISO 20022 successor through one or more correspondent banks, while a money transfer operator may route through prefunded payout partners in the destination country. Each path has its own fees, cut-off times and foreign-exchange spread, so operators pick routes per corridor and sometimes per payment.
Who decides the route
Routing decisions sit with different parties depending on the payment:
- Merchants and their providers. A merchant, or the payment orchestration layer it uses, chooses between acquirers and processors, often by country, currency or card type.
- Switches and networks. A payment switch applies routing tables that map BIN ranges or account identifiers to destinations.
- Issuers and banks. Banks decide which networks a card carries and which rails they connect to, which limits the routes available downstream.
- Regulators. Rules on co-badged cards, network exclusivity and access to instant schemes shape which routes must be offered.
What a routing choice affects
The route changes three things. The first is cost: interchange, network fees and processor margins differ between networks and acquirers. The second is approval: an issuer may approve more often on a local acquiring route than on a cross-border one, so a route that is cheaper on paper can lose sales through a higher payment decline rate. The third is resilience: if one processor has an outage, a merchant with a second route can switch traffic instead of suffering a payment failure on every attempt.
Routing also affects later stages. The route used for authorization normally determines where payment capture, clearing and refunds must go, because those follow-up messages have to reference the original transaction on the same network. That is why routing design is linked to reconciliation and dispute handling as well as to price.