Cost-aware routing is a payment routing strategy that sends each transaction to the eligible provider expected to process it at the lowest total cost, counting interchange, scheme fees, acquirer markup, currency conversion and the revenue lost when a payment is declined. It runs after capability-based routing has removed ineligible providers, then estimates fees from card brand, type, issuing country and currency. On a €100 German consumer debit payment, an interchange++ acquirer may cost €0.55 against €1.40 at a blended 1.4%, yet a provider with a higher approval rate can still win once lost margin is priced in. Fee tables drift, so reported routing savings should be checked against invoices before they influence a valuation.
What is cost aware routing
It is a ranking step that runs after capability-based routing has removed providers unable to take the payment. For each remaining provider, the engine estimates the fee for this specific card and amount, using attributes such as card brand, debit or credit, consumer or commercial, issuing country and currency, and picks the lowest.
How does cost based payment routing work
Pricing models drive the result. Take a €100 payment on a German consumer debit card. Acquirer A charges a blended 1.4%, or €1.40. Acquirer B prices interchange++: EU interchange on consumer debit is capped at 0.2% (€0.20), scheme fees add perhaps €0.10, and B's markup of 0.25% adds €0.25, for €0.55 in total. B wins. Now take a US-issued corporate credit card: interchange++ passes through much higher cross-border and commercial-card interchange, and A's flat 1.4% may be cheaper. The same two acquirers win different halves of the traffic.
Payment routing optimization by cost: the full equation
Fees are only half the calculation. Expected cost equals the processing fee plus the probability of decline multiplied by the value of a lost sale. Suppose A charges €0.55 with an 88% approval rate, and C charges €0.70 with 93%. On a €100 order carrying €20 of margin, A's expected decline loss is 12% × €20 = €2.40, against C's 7% × €20 = €1.40. C costs €0.15 more to process and saves €1.00 in lost margin. Smart routing engines blend both figures; routing on fees alone often lowers the processing bill while cutting revenue.
Choosing the network on debit cards
Some markets give the merchant a choice of network on the same card. In the US, Regulation II requires debit cards to be enabled on at least two unaffiliated networks, and since July 2023 that explicitly covers card-not-present payments, so merchants can route to the cheaper network. Australia promotes least-cost routing on dual-network debit cards between eftpos and the international schemes. In the EU, the Interchange Fee Regulation lets merchants pick the brand on co-badged cards, such as Cartes Bancaires alongside Visa.
Where cost models go wrong
Fee tables drift as schemes change fees and acquirers reprice, and cross-border and foreign exchange charges are often missing from the model entirely. Moving all volume to the cheapest acquirer can also cost volume-tier discounts elsewhere and remove fallback capacity. The routing savings a payment business reports are worth checking against actual invoices before anyone pays for them in a valuation.