American Express and Discover: The Closed LoopsNarrow moat

Mastercard (MA) — moat facet

A network that is also the bank keeps the whole fee, and now one of the largest American banks owns one.

American Express and Discover compete with a different design. In a closed or partly closed network the company that runs the network also issues the cards, so it keeps both the issuer's and the network's share of the merchant fee and needs no rebate to win a bank. Mastercard's filing notes that some competitors have different business models that may provide an advantage in pricing1.

US card purchase volume, 2025Visa and Mastercard $9.986tn — 87%Amex and Discover $1.477tn — 13%Nilson Report 2025; Amex and Discover calculated
Small in volume, and now owned by a bank.

Their share of American spending is smaller. The four networks' cards carried $11.463 trillion of purchase volume in the United States in 20252; Visa and Mastercard together carried $9.986 trillion3, leaving about $1.477 trillion for American Express and Discover4, roughly 13%5.

The closed loop matters now because of who owns it. Discover belongs to Capital One, which moved its debit cards from Mastercard onto the Discover network after closing the acquisition67. A bank that owns a closed loop can take volume from the open networks without negotiating with them. The details are on the moat page about the portfolio that left.

Mastercard's filing also notes that a number of its own customers issue American Express-, China UnionPay- or Discover-branded cards in a four-party manner8. The rival brands are sometimes on cards Mastercard's customers issue.

The closed-loop model has an obvious cost: it has to find its own cardholders and carry their credit risk. That is why American Express and Discover never overtook the open networks despite keeping the whole fee. Mastercard's open model spreads the credit risk across thousands of issuers and collects a smaller share of each transaction from a much larger base; in 2025 gross dollar volume on its cards was $10,632 billion9. The closed loops are a threat only when a bank that already has millions of cardholders owns one.

The competition here is narrow in scale and structural in consequence. The sign to watch is whether another large issuer moves a portfolio to a closed loop it controls; if none does by 2028, Capital One will look like an exception.

Moat trajectory: Narrowing

Capital One's ownership of Discover turned a small rival into a route out for a large customer.

The number that tests this moat
Moat Explorer calc
Amex and Discover share of US purchase volume
About 13% (2025: $1.477tn of $11.463tn)

The closed loops' share; a rising share after Capital One's migrations would mean the open networks are losing volume to them.

How it's calculated: Four-network US purchase volume less Visa and Mastercard (Nilson Report 2025), divided by the four-network total.
Source: Nilson Report, global brand cards in the US, 2025 ↗
References
  1. ReportedMastercard's filing notes that some competitors have different business models that may provide an advantage in pricing.
    Mastercard Form 10-K for fiscal 2025 - Item 1 business: the network, competition, tokenization, account-based payments and human capital. — FY2025 · publ. 11 February 2026 · source ↗
  2. Third-party estimateThe four networks' cards carried $11.463 trillion of purchase volume in the United States in 2025; Visa and Mastercard together carried $9.986 trillion, leaving about $1.477 trillion for American Express and Discover, roughly 13%.
    The Nilson Report, Global Brand Cards in the US - 2025: purchase volume on the four networks. — 2025 · publ. 2026 · source ↗
  3. Third-party estimateThe four networks' cards carried $11.463 trillion of purchase volume in the United States in 2025; Visa and Mastercard together carried $9.986 trillion, leaving about $1.477 trillion for American Express and Discover, roughly 13%.
    The Nilson Report, Mastercard and Visa Cards in the US - 2025: purchase volume $7.028 trillion on Visa and $2.958 trillion on Mastercard. — 2025 · publ. 2026 · source ↗
  4. Moat Explorer calcThe four networks' cards carried $11.463 trillion of purchase volume in the United States in 2025; Visa and Mastercard together carried $9.986 trillion, leaving about $1.477 trillion for American Express and Discover, roughly 13%.
    Moat Explorer calculation from Mastercard's reported figures ($ millions unless stated). Gross payment network assessments 2025: 11,029 + 12,021 + 15,930 + 1,018 = 39,998; rebates 20,522 / 39,998 = 51.3%; 2024: 10,245 + 10,181 + 13,602 + 936 = 34,964, 17,629 / 34,964 = 50.4%; 2023: 15,182 / (15,824 + 15,182) = 49.0%; 2022: 8,794 + 6,597 + 10,646 + 766 = 26,803, 12,445 / 26,803 = 46.4%; 2021: 10,476 / (11,943 + 10,476) = 46.7%. Q2 2026: 5,997 / (5,451 + 5,997) = 52.4%; gross assessments growth (5,451 + 5,997) / (4,945 + 5,997 / 1.22) - 1 = about 16%. Old basis: 3,980 / 13,647 = 29.2% (2015); 8,315 / 23,616 = 35.2% (2020). Rebates 20,522 / 3,980 = 5.2 times; net revenue 32,791 / 9,667 = 3.4 times. Rebates against gross revenue 2025: 20,522 / (32,791 + 20,522 = 53,313) = 38.5%; Visa 15,751 / (40,000 + 15,751 = 55,751) = 28.3%; difference 20,522 - 15,751 = 4,771. US share: 2,958 / (2,958 + 7,028) = 29.6%; four networks 2,958 / 11,463 = 25.8%; Amex and Discover 11,463 - 9,986 = 1,477, 1,477 / 11,463 = 12.9%. Outside the US 100% - 29% = 71%. Cross-border assessments 12,021 / 3,498 = 3.4 times; cross-border volume fees 3,512 / 5,606 - 1 = -37.4%; 12,021 x 0.37 = 4,448. Services share of net revenue: 5,404 / 15,301 = 35.3% (2020); 6,941 / 18,884 = 36.8%; 7,879 / 22,237 = 35.4%; 9,274 / 25,098 = 37.0%; 10,832 / 28,167 = 38.5%; 13,315 / 32,791 = 40.6% (2025); 3,826 / 9,277 = 41.2% (Q2 2026); payment network 19,476 / 32,791 = 59.4%. Growth: payment network 11,943 / 9,897 - 1 = 21%, 14,358 / 11,943 - 1 = 20%, 15,824 / 14,358 - 1 = 10%, 17,335 / 15,824 - 1 = 10%, 19,476 / 17,335 - 1 = 12%; 19,476 / 9,897 = 2.0 times; services 7,879 / 6,941 - 1 = 14% (2022), 13,315 / 5,404 = 2.5 times; growth gap Q2 2026 20% - 10% = 10 points; acquisitions 3 / 23 = 13%. Operating margin: 5,078 / 9,667 = 52.5% (2015); 6,622 / 12,497 = 53.0% (2017); 7,282 / 14,950 = 48.7% (2018); 9,664 / 16,883 = 57.2% (2019); 8,081 / 15,301 = 52.8% (2020); 12,264 / 22,237 = 55.2% (2022). Headcount 39,800 / 13,400 = 3.0 times; net revenue 32,791 / 12,497 = 2.6 times (2017-2025). Capital spending 489 + 726 = 1,215; 1,215 / 32,791 = 3.7%; free cash flow 17,648 - 1,215 = 16,433; returned 11,727 + 2,756 = 14,483, 14,483 / 16,433 = 88%. Net debt 30 June 2026: 2,459 + 22,184 - 11,291 = 13,352. Diluted shares 906 / 1,137 - 1 = -20.3%; EPS 16.52 / 3.35 = 4.9 times, (16.52 / 3.35)^(1/10) - 1 = 17.3% a year; net income 14,968 / 3,808 = 3.9 times; net revenue (32,791 / 9,667)^(1/10) - 1 = 13.0% a year. Year-end P/E (market value over net income): 109.31 / 3.808 = 28.7 (2015); 160.24 / 3.915 = 40.9 (2017); 301.24 / 8.118 = 37.1 (2019); 353.05 / 8.687 = 40.6 (2021); 334.33 / 9.930 = 33.7 (2022); 483.30 / 12.874 = 37.5 (2024); 512.65 / 14.968 = 34.2 (2025); earnings yield 1 / 31.13 = 3.2%. Litigation provision against net income: 504 / 14,968 = 3.4%; 539 / 11,195 = 4.8%; 680 / 12,874 = 5.3%. Tax: pre-tax income 2025 14,968 + 3,610 = 18,578; (19.4% - 15.6%) x 18,578 = about 706. Amortised incentives 2,098 / 19,476 = 10.8%. Five-customer net revenue 6.9 bn. BVNK 1,500 / 11,727 = 13% of 2025 buybacks; acquisitions since 2020 809 + 861 + 325 + 2,700 + 1,500 = 6,195, 1,500 / 6,195 = 24%. Recorded Future 2,700 / 14,968 = 18%. Commercial gross dollar volume 1,405 / 10,632 = 13.2%. Property, equipment and right-of-use assets 1,168 + 1,135 = 2,303 - revenue mix, margins, geography and competitors. — 2015-2026 · publ. September 2026 · source ↗
    Method: Arithmetic on figures reported in Mastercard's Forms 10-K, 10-Q, results releases, the Visa 10-K and the Nilson Report; operands shown in the source line.
  5. Moat Explorer calcThe four networks' cards carried $11.463 trillion of purchase volume in the United States in 2025; Visa and Mastercard together carried $9.986 trillion, leaving about $1.477 trillion for American Express and Discover, roughly 13%.
    Moat Explorer calculation from Mastercard's reported figures ($ millions unless stated). Gross payment network assessments 2025: 11,029 + 12,021 + 15,930 + 1,018 = 39,998; rebates 20,522 / 39,998 = 51.3%; 2024: 10,245 + 10,181 + 13,602 + 936 = 34,964, 17,629 / 34,964 = 50.4%; 2023: 15,182 / (15,824 + 15,182) = 49.0%; 2022: 8,794 + 6,597 + 10,646 + 766 = 26,803, 12,445 / 26,803 = 46.4%; 2021: 10,476 / (11,943 + 10,476) = 46.7%. Q2 2026: 5,997 / (5,451 + 5,997) = 52.4%; gross assessments growth (5,451 + 5,997) / (4,945 + 5,997 / 1.22) - 1 = about 16%. Old basis: 3,980 / 13,647 = 29.2% (2015); 8,315 / 23,616 = 35.2% (2020). Rebates 20,522 / 3,980 = 5.2 times; net revenue 32,791 / 9,667 = 3.4 times. Rebates against gross revenue 2025: 20,522 / (32,791 + 20,522 = 53,313) = 38.5%; Visa 15,751 / (40,000 + 15,751 = 55,751) = 28.3%; difference 20,522 - 15,751 = 4,771. US share: 2,958 / (2,958 + 7,028) = 29.6%; four networks 2,958 / 11,463 = 25.8%; Amex and Discover 11,463 - 9,986 = 1,477, 1,477 / 11,463 = 12.9%. Outside the US 100% - 29% = 71%. Cross-border assessments 12,021 / 3,498 = 3.4 times; cross-border volume fees 3,512 / 5,606 - 1 = -37.4%; 12,021 x 0.37 = 4,448. Services share of net revenue: 5,404 / 15,301 = 35.3% (2020); 6,941 / 18,884 = 36.8%; 7,879 / 22,237 = 35.4%; 9,274 / 25,098 = 37.0%; 10,832 / 28,167 = 38.5%; 13,315 / 32,791 = 40.6% (2025); 3,826 / 9,277 = 41.2% (Q2 2026); payment network 19,476 / 32,791 = 59.4%. Growth: payment network 11,943 / 9,897 - 1 = 21%, 14,358 / 11,943 - 1 = 20%, 15,824 / 14,358 - 1 = 10%, 17,335 / 15,824 - 1 = 10%, 19,476 / 17,335 - 1 = 12%; 19,476 / 9,897 = 2.0 times; services 7,879 / 6,941 - 1 = 14% (2022), 13,315 / 5,404 = 2.5 times; growth gap Q2 2026 20% - 10% = 10 points; acquisitions 3 / 23 = 13%. Operating margin: 5,078 / 9,667 = 52.5% (2015); 6,622 / 12,497 = 53.0% (2017); 7,282 / 14,950 = 48.7% (2018); 9,664 / 16,883 = 57.2% (2019); 8,081 / 15,301 = 52.8% (2020); 12,264 / 22,237 = 55.2% (2022). Headcount 39,800 / 13,400 = 3.0 times; net revenue 32,791 / 12,497 = 2.6 times (2017-2025). Capital spending 489 + 726 = 1,215; 1,215 / 32,791 = 3.7%; free cash flow 17,648 - 1,215 = 16,433; returned 11,727 + 2,756 = 14,483, 14,483 / 16,433 = 88%. Net debt 30 June 2026: 2,459 + 22,184 - 11,291 = 13,352. Diluted shares 906 / 1,137 - 1 = -20.3%; EPS 16.52 / 3.35 = 4.9 times, (16.52 / 3.35)^(1/10) - 1 = 17.3% a year; net income 14,968 / 3,808 = 3.9 times; net revenue (32,791 / 9,667)^(1/10) - 1 = 13.0% a year. Year-end P/E (market value over net income): 109.31 / 3.808 = 28.7 (2015); 160.24 / 3.915 = 40.9 (2017); 301.24 / 8.118 = 37.1 (2019); 353.05 / 8.687 = 40.6 (2021); 334.33 / 9.930 = 33.7 (2022); 483.30 / 12.874 = 37.5 (2024); 512.65 / 14.968 = 34.2 (2025); earnings yield 1 / 31.13 = 3.2%. Litigation provision against net income: 504 / 14,968 = 3.4%; 539 / 11,195 = 4.8%; 680 / 12,874 = 5.3%. Tax: pre-tax income 2025 14,968 + 3,610 = 18,578; (19.4% - 15.6%) x 18,578 = about 706. Amortised incentives 2,098 / 19,476 = 10.8%. Five-customer net revenue 6.9 bn. BVNK 1,500 / 11,727 = 13% of 2025 buybacks; acquisitions since 2020 809 + 861 + 325 + 2,700 + 1,500 = 6,195, 1,500 / 6,195 = 24%. Recorded Future 2,700 / 14,968 = 18%. Commercial gross dollar volume 1,405 / 10,632 = 13.2%. Property, equipment and right-of-use assets 1,168 + 1,135 = 2,303 - revenue mix, margins, geography and competitors. — 2015-2026 · publ. September 2026 · source ↗
    Method: Arithmetic on figures reported in Mastercard's Forms 10-K, 10-Q, results releases, the Visa 10-K and the Nilson Report; operands shown in the source line.
  6. ReportedDiscover belongs to Capital One, which moved its debit cards from Mastercard onto the Discover network after closing the acquisition.
    PaymentsJournal, After Moving Debit Cards to Discover, Capital One Turns to Credit Card Migration. — July 2026 · publ. 22 July 2026 · source ↗
  7. Third-party estimateDiscover belongs to Capital One, which moved its debit cards from Mastercard onto the Discover network after closing the acquisition.
    Tech Times, Capital One Found a $1 Billion Loophole in Debit Fee Law: Big Banks Are Copying the Play - 25 million debit cards on Discover, the $35.3 billion Discover acquisition, and analyst estimates of the interchange effect. — July 2026 · publ. 23 July 2026 · source ↗
  8. ReportedMastercard's filing also notes that a number of its own customers issue American Express-, China UnionPay- or Discover-branded cards in a four-party manner.
    Mastercard Form 10-K for fiscal 2025 - Item 7 MD&A: net revenue by category, key metrics, rebates, geography and the five largest customers. — FY2025 · publ. 11 February 2026 · source ↗
  9. ReportedMastercard's open model spreads the credit risk across thousands of issuers and collects a smaller share of each transaction from a much larger base; in 2025 gross dollar volume on its cards was $10,632 billion.
    Mastercard fourth-quarter and full-year 2025 results release, Form 8-K exhibit 99.1 - statements, cash flow and operating metrics. — FY2025 · publ. 29 January 2026 · source ↗
Sources
Generated September 25, 2026