How Interchange Works in the Four-Party Scheme
The four-party card scheme is the dominant structure for consumer card payments globally, and it is the structure used by Visa and Mastercard. The four parties are the cardholder, the issuer, the merchant and the acquirer. Understanding the direction and magnitude of the financial flows between these parties is the foundation of any interchange revenue model.
Four-Party Scheme: Cash Flows
The acquirer pays the interchange to the issuer via the scheme. The acquirer retains its margin (MSC minus interchange minus scheme fees) and the remainder is the merchant's net proceeds.
The critical insight for an issuer's revenue model is that interchange flows from the acquirer to the issuer, not from the cardholder. The cardholder pays the full purchase amount to the merchant; the merchant pays the Merchant Service Charge (MSC) to the acquirer; the acquirer retains its margin and passes the interchange component to the issuer via the scheme's clearing and settlement system. The issuer therefore earns interchange on every transaction made on its cards, funded ultimately by the merchant through the MSC.
The Visa and Mastercard schemes publish interchange rate tables periodically. These tables set the rates that apply for different combinations of card type, transaction type (domestic versus cross-border), merchant category code (MCC) and cardholder presence (card-present versus card-not-present). The published rates are the regulated maximums for consumer cards and the standard rates for commercial cards; issuers cannot exceed these rates, but bilateral agreements between large issuers and acquirers may result in different effective rates in specific circumstances.
The Regulatory Caps
The EU Interchange Fee Regulation (Regulation (EU) 2015/751) imposed hard caps on interchange rates for consumer card transactions within the EU/EEA. The UK retained these caps post-Brexit, and as at July 2024 they remain in force for UK domestic transactions. The caps are:
The PSR's MR22/1.6 investigation into cross-border interchange fees is a live regulatory issue of material significance for UK card issuers with European cardholders or UK acquirers processing European cards. Following Brexit, Visa and Mastercard both increased the interchange rates applicable to UK card transactions at EU merchants and EU card transactions at UK merchants, with Visa increasing UK debit card rates at EU merchants from 0.2% to 1.15% and Mastercard making similar changes. These increases represented significant revenue changes for affected issuers and acquirers, and the PSR's investigation could result in remedies including rate reductions.
How to Model Interchange Revenue
A simple single-rate interchange model takes total card spend volume and multiplies it by a single blended interchange rate. This is acceptable for a high-level projection but will be materially inaccurate as soon as the portfolio mix changes, because the key drivers of blended interchange rate are not static.
A robust interchange model requires the following inputs at minimum.
| Input Driver | Why It Matters | Rate Range (UK, July 2024) |
|---|---|---|
| Domestic consumer debit | Capped at 0.2%. Lowest-rate category. Typically the highest volume for consumer issuers. | 0.2% |
| Domestic consumer credit | Capped at 0.3%. Higher rate than debit. | 0.3% |
| Commercial debit/credit (domestic) | Uncapped. Rates set by scheme. Materially higher than consumer caps. | 0.5%–1.5%+ |
| Cross-border consumer (UK→EU) | Post-Brexit rates. PSR review ongoing. Material uplift vs domestic. | 1.15% (Visa debit) / 1.5% (MC credit) |
| Card-not-present premium | Online transactions attract a higher interchange rate than in-person transactions in most scheme tables. | +0.1%–0.2% on base rate |
| MCC-specific rates | Specific merchant categories (travel, fuel, government, charity) attract different rates that may be above or below the standard rate. | Varies widely by MCC |
| Blended rate (consumer domestic example) | Weighted average across domestic mix for a consumer debit/credit portfolio | ~0.22%–0.26% |
The blended interchange rate is the weighted average of all applicable rates across the full transaction portfolio. A fintech issuer with a predominantly domestic consumer debit book will have a blended rate close to the 0.2% cap. A corporate card issuer with high international spend and a commercial card product will have a materially higher blended rate. The model must explicitly capture the portfolio mix and recalculate the blended rate as the mix changes over time.
"A single-rate interchange model is almost always wrong. The portfolio mix between domestic consumer, cross-border, commercial and card-not-present transactions can easily move the blended rate by 50 to 100 basis points, which on a portfolio of £500m annual spend is a £2.5m to £5m revenue variance. This is not a rounding error."
Net Interchange: Gross Minus Scheme Fees
The interchange rate that flows from the acquirer to the issuer is the gross interchange. The issuer then pays scheme fees to Visa or Mastercard based on the same transaction volumes. The net interchange — the amount the issuer actually retains — is gross interchange minus scheme fees.
Scheme fees for issuers fall into several categories.
- Assessment fees: a percentage of net transaction value processed on the scheme. Typically 0.05% to 0.15% of transaction value depending on volume tier and scheme.
- Authorisation fees: a flat fee per authorisation request sent to the issuer, regardless of whether the authorisation is approved. Typically a few pence per transaction.
- Fraud monitoring fees: fees associated with the scheme's fraud monitoring and compliance programmes. Variable depending on the issuer's fraud performance.
- Network access fees: recurring fees for access to the scheme's infrastructure, licensing and settlement services.
- Data integrity and compliance fees: fees associated with the scheme's data security standards (PCI DSS compliance fees, tokenisation fees).
The aggregate of scheme fees typically represents 30% to 60% of gross interchange for a consumer debit issuer, where the gross interchange is already at the 0.2% regulatory cap. The resulting net interchange is therefore in the range of 0.08% to 0.14% of transaction value for domestic consumer debit. For commercial card transactions where the gross interchange is higher (0.5% to 1.5%+), the scheme fees are a smaller proportion of the gross, and net interchange is more favourable.
The Interchange P&L Structure for Investors
When presenting interchange-driven revenue to investors, the P&L structure should be explicit about the distinction between gross interchange and net interchange, and about the scheme fees that sit in COGS. Investors who are not familiar with payment economics will often assume that the interchange rate listed in the regulatory table (0.2% or 0.3%) is the net revenue; they need to understand that scheme fees materially reduce this.
Key Takeaways
- Interchange flows from the acquirer to the issuer via the scheme. It is funded by the merchant through the Merchant Service Charge. The issuer earns interchange on every transaction made on its cards.
- UK domestic consumer debit interchange is capped at 0.2%; consumer credit at 0.3% under the retained EU IFR. Commercial card interchange is uncapped and materially higher.
- A robust interchange model has 10 to 15 rate inputs and a portfolio mix driver. The blended rate changes materially as the mix between domestic consumer, cross-border, commercial and card-not-present transactions evolves.
- Net interchange is gross interchange minus scheme fees. Scheme fees typically represent 30% to 60% of gross interchange for a domestic consumer debit portfolio. Net interchange is 40% to 70% of gross interchange.
- The PSR's MR22/1.6 investigation into post-Brexit cross-border interchange rates is a live uncertainty for UK issuers with European transaction exposure. Model this as a scenario rather than a known rate.
- When presenting to investors, be explicit about the gross-to-net reconciliation. Investors unfamiliar with payment economics will need to understand the scheme fee deduction before they can evaluate the unit economics of the card programme.
