# What is a card network?

URL: https://www.paydude.io/resources/what-is-a-card-network
Type: Guide
Published: 2026-09-02 · Updated: 2026-09-02
Summary: Card networks operate the rails, set interchange and charge assessments. How the four-party model works, and why Amex and Discover are different.

**A card network operates the rails that carry a transaction between your bank and your customer's bank.** Visa, Mastercard, American Express and Discover set the rules, set interchange rates, and charge a small assessment on every transaction. They do not issue most cards and they do not hold your money.

## Summary

Networks set interchange but do not receive it — the issuing bank does. They earn from assessments, typically 0.13–0.15% of volume. Visa and Mastercard use a four-party model and issue no cards themselves. Amex and Discover are both network and issuer, which is why they price differently.

## The four-party model

Visa and Mastercard sit in the middle of four parties and issue nothing themselves.

**Who is who in a Visa or Mastercard transaction**

| Party | Role |
| --- | --- |
| Cardholder | Your customer |
| Issuing bank | Gave the customer their card; approves or declines |
| Card network | Operates the rails and sets the rules |
| Acquiring bank | Holds your merchant account and receives the funds |

The network's role is coordination: it defines the message formats, the dispute process, the security standards and the interchange schedule that every issuer and acquirer follows. Its revenue comes from assessments, not from interchange.

## Why Amex and Discover are different

American Express and Discover operate a **three-party model**: they are the network and, for most of their cards, the issuer as well. With no separate issuing bank there is no interchange to pay — Amex simply sets the entire merchant rate itself.

That is the historical reason Amex cost noticeably more to accept. The gap has narrowed as Amex has pushed for wider acceptance, and most modern flat-rate processors now charge the same published rate across all four networks.

> **Flat-rate pricing hides the difference:** On flat-rate pricing you pay 2.9% whether the customer uses a debit card costing the processor 0.3% or an Amex costing considerably more. The processor absorbs the variance and prices for the average — which is precisely what you are paying for.

## What networks charge

- **Assessment fee** — roughly 0.13–0.15% of transaction value.
- **Per-transaction network fees** — a few cents, under various names.
- **Cross-border fees** — when the card and the merchant are in different countries.
- **Currency conversion** — when the transaction currency differs from the card's.

Like interchange, none of this is negotiable. It is the same for every merchant regardless of processor — see [credit card processing fees, explained](https://www.paydude.io/resources/credit-card-processing-fees-explained) for how the three components stack up.

**One published rate across all networks** No surprise surcharge because a customer paid with the wrong card. — [See pricing](https://www.paydude.io/pricing)

## Frequently asked questions

### Do card networks make money from interchange?

No. Interchange goes to the bank that issued the card. Networks earn from assessment fees, typically 0.13–0.15% of volume, plus various per-transaction and cross-border charges.

### Why does American Express cost more to accept?

Amex operates a three-party model — it is both the network and the issuer, so there is no separate interchange to pay and Amex sets the whole rate itself. Historically that produced higher merchant fees, funding a more affluent cardholder base and richer rewards.

### What is the difference between a card network and a payment processor?

The network operates the rails and sets the rules that everyone follows. The processor is the company you contract with to send transactions over those rails. You have a commercial relationship with a processor; you do not with Visa.

### Can I accept some networks and not others?

Yes. Some merchants decline American Express because of its historically higher rates, though the gap has narrowed considerably. Declining Visa or Mastercard is rarely practical given their share of cards in circulation.