The short answer
A card network (sometimes called a "card scheme" internationally) is the organization that operates the rails between card-issuing banks and acquiring banks. They route authorizations and clearings, set the interchange + assessment fees, publish the operating rules, and run the chargeback / dispute systems. The four that matter in the US are Visa, Mastercard, American Express, and Discover. Globally add UnionPay (China) and JCB (Japan).
How the networks are structured
- Visa + Mastercard: open-loop. Thousands of issuing banks, thousands of acquirers. The network is the connector. Visa and Mastercard don't issue cards directly — they license the brand to banks that do.
- American Express: closed-loop (traditionally). Amex historically issued cards AND acquired merchants directly — one entity for both sides. In the 2010s+ they opened to third-party acquirers. Still, Amex often has its own separate merchant agreement.
- Discover: closed-loop (traditionally). Same pattern as Amex. Discover Card is issued by Discover Bank.
- UnionPay / JCB: open-loop, regional. Dominant in China / Japan, relevant for cross-border.
What the networks do on every transaction
- Route the authorization. Merchant → acquirer → network → issuer → approval/decline → back.
- Enforce interchange. The acquirer pays interchange to the issuer; the network mandates the rate. Rates vary by card, merchant, and transaction type.
- Collect assessments. Network's own fee — Visa assessment is 0.14%, Mastercard is 0.1375% on credit. Small, but adds up.
- Handle the chargeback flow. Issuer files → network routes → acquirer responds → representment, arbitration, pre-arbitration all happen on network rails.
- Enforce the rules. 1,000+ pages of operating rules per network. Violations carry fines and program enrollment.
Key network programs operators should know
- Visa VAMP (2025+): dispute + fraud monitoring. See VAMP entry.
- Mastercard ECM: excessive chargeback program. See ECM entry.
- Visa Compelling Evidence 3.0: modernized representment rules (April 2023). See compelling evidence.
- Mastercard First-Party Trust: representment for first-party fraud claims.
- Visa Claims Resolution (VCR): workflow for chargebacks on Visa.
- 3DS 2.0: issuer-authentication protocol for CNP fraud reduction.
How network fees show up on your statement
- Visa: 0.14% assessment + $0.0195 Acquirer Processing Fee + $0.0018 Kilobyte Fee + $0.10-$0.25 per-transaction misc.
- Mastercard: 0.1375% assessment + 0.01% NABU + $0.0195 per-transaction + international surcharges
- Amex: varies by program — OptBlue vs. direct Amex relationship — typically 2.5%+ effective
- Discover: similar structure to Visa/Mastercard
What operators can and can't negotiate
- Can't negotiate: interchange rates, network assessments. These are set by the network, take them or leave them.
- Can negotiate: processor margin (the markup above interchange + assessments). With volume, 20-50 basis points is common.
- Can avoid: bad MCC codes, penalty programs, network fines — all driven by operator hygiene, not negotiation.
Why multiflow operators care about the network layer
Most of your effective rate is network cost, not processor margin. Understanding which cost is interchange (non-negotiable), which is assessment (non-negotiable), and which is processor margin (negotiable) is how you know whether you're getting a fair deal. multiflow operator statements break fees out by category so you can see exactly where every basis point goes.