Mastering Payment Systems: 88 Diagrams and 66 Key Concepts Explained

1. Essence of Payment

Payment is fundamentally the transfer of funds from a payer to a payee.

Payee and payer : can be individuals, enterprises, or banks.

Funds : cash, bank deposits, or balance in a payment institution.

Transfer : change in debt ownership.

Tools : bank cards, checks, mobile or online payment methods.

2. Payment vs Transaction

Transaction is the exchange of value; payment is the transfer of money.

Pure transaction : value exchange without money.

Pure payment : fund transfer without goods or services.

Transaction‑based payment : money exchanged for goods/services.

3. Payment Process

Payment can be divided into three stages: transaction, clearing, and settlement.

Transaction : user identity verification, order creation, and payment initiation.

Clearing : receipt, split, and netting of payment instructions.

Settlement : fund allocation based on clearing results.

4. Direct and Indirect Connection

Institutions can connect via direct (straight‑through) or indirect (through a third party) modes.

Direct : interface directly with payment instructions.

Indirect : route payment instructions through a third‑party institution.

5. Payment Models

Various payment models have emerged over the years.

First‑party payment : cash, face‑to‑face hand‑over.

Second‑party payment : bank transfers, improving safety and convenience.

Third‑party payment : licensed third‑party institutions transfer funds to merchants.

Fourth‑party payment : aggregation platforms route funds to payees.

6. Clearing Modes

Clearing can be intra‑institution (same institution) or inter‑institution (different institutions). It can also be real‑time full‑amount clearing or delayed net‑amount clearing (single‑ or multi‑party).

Intra‑institution clearing : payer and payee accounts belong to the same institution.

Inter‑institution clearing : payer and payee accounts belong to different institutions.

7. Three‑Party Ecosystem

Payment organizations are divided into acquiring side (providing collection services) and account side (providing user funds accounts, e.g., WeChat, Alipay).

8. Settlement Types (PVP/DVP/Agency)

PVP (Payment Versus Payment) settles simultaneously with foreign exchange; DVP (Delivery Versus Payment) settles securities with cash; agency settlement involves a third‑party holding funds until conditions are met.

9. Composite and Merged Payments

Composite payment uses multiple methods (internal coupons/balance + external channels). Merged payment aggregates several sub‑orders into a single payment, common in travel or e‑commerce.

10. Split Payments

When the amount exceeds single‑transaction limits, the order is split into multiple payments; the order is considered successful only after all splits are completed.

11. Recharge, Withdrawal, Transfer

Recharge moves funds from a high‑credit account (e.g., bank) to a low‑credit account (e.g., payment wallet). Withdrawal does the opposite. Transfer moves funds between accounts of the same credit level.

12. Payment Channels

Channels include collection, payment, refund, authentication, and real‑name verification. Examples: third‑party quick‑pay, UnionPay quick‑pay, bank quick‑pay, online banking, direct‑debit, WeChat Pay, etc.

13. Payment Accounting

After a successful payment, accounting records involve payment, transaction, and marketing layers. Example journal entry: Debit Bank Deposit 80, Debit Sales Expense 20 (coupon), Credit Merchant Receivable 100.

14. Core Payment Panorama

Payment involves multiple organizations and systems: merchant platform, payment institution, clearing institution, and banks. The flow moves from user order to final settlement across these layers.

15. Settlement Products

Settlement products include T+1, D+1, D0, H0, S0, and TD (cross‑day) settlements, each defining the timing and method of fund transfer to merchants.

16. Fee and Cost Models

Merchant fees can be internal or external; channel costs may be fixed, percentage‑based, tiered, interest‑based, or UnionPay‑tiered.

17. Reconciliation

Three reconciliation models: transaction reconciliation (platform vs channel records), fund reconciliation (expected vs actual receipts/payments), and balance adjustment (system balance vs actual account balance).

18. Hot Account Solutions

Strategies for high‑concurrency accounts include rate limiting, aggregation, buffering, caching, sub‑account sharding, front‑end buffering, and system performance upgrades.

19. Two‑Level Clearing (Secondary Clearing)

Secondary clearing occurs when a qualified clearing institution settles funds to a platform that lacks clearing qualification, which then settles to its sub‑merchants, creating a risk of “naked” funds.

20. Risk Management

Ensuring fund safety requires adhering to the principle that channel payment must succeed before accounting, and merchant deduction must succeed before disbursement.