🏦 Banking Domain Knowledge Base
A comprehensive, engineer-focused reference for payment systems, ISO 20022 messaging, core banking concepts, and Australian payment infrastructure. Built for Java/Spring developers working in the payments domain.
What's in This Knowledge Base?
| Section | Topics Covered |
|---|---|
| ISO 20022 Messages | pain.001, pain.002, pacs.008, pacs.002, camt.053, camt.054 |
| Payment Flows | Inbound, Outbound, On-Us, Off-Us |
| Payment Rails | NPP, SWIFT, BECS/Direct Debit, BPAY, RTGS, PayTo |
| Parties & Institutions | Debtor, Creditor, FIs, Correspondent Banks |
| Accounting & Posting | Debit/Credit Post, Debit Reversal, Payment Return |
| Clearing & Settlement | DNS, RTGS, ESA, Liquidity |
| Risk & Compliance | Fraud, Sanctions, AML/CTF, KYC |
| Operations | Reconciliation, Exceptions & Investigations, FX |
| Modern Banking | Open Banking/CDR, ISO 20022 Migration, Account Types |
End-to-End Payment Lifecycle
The diagram below shows a complete outbound off-us NPP credit transfer — the most common domestic payment type in Australia.
┌─────────────────────────────────────────────────────────────────────────────┐
│ PAYMENT LIFECYCLE │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ORIGINATION DEBTOR BANK CREDITOR BANK │
│ │
│ Customer Receive pain.001 Receive pacs.008 │
│ submits ──────► Validate & Auth ──────► Validate Schema │
│ pain.001 Balance Check Duplicate Check │
│ Sanctions Screen Sanctions Screen │
│ Fraud Assessment Fraud Assessment │
│ Debit Posting Account Lookup │
│ Build pacs.008 Credit Posting │
│ Submit to NPP ◄────── Send camt.054 ──► Cdtr │
│ Receive pacs.002 (CRDT notification) │
│ Send camt.054 ──────► │
│ (DBIT notification) Dbtr │
│ Send pain.002 ──────► │
│ (status report) Customer │
│ │
│ SETTLEMENT: RBA Fast Settlement Service (FSS) — real-time gross │
└─────────────────────────────────────────────────────────────────────────────┘
ISO 20022 Message Chain
Customer ──[pain.001]──► Debtor Bank ──[pacs.008]──► Network ──[pacs.008]──► Creditor Bank
◄─[pain.002]─── ◄─[pacs.002]─── │
[camt.054]
[camt.054]──► Debtor Customer │
Creditor Customer
If undeliverable:
Debtor Bank ◄─[pacs.004]────────────────────────────────────── Creditor Bank
──[camt.054 return]──► Debtor Customer
Key ID Fields — Traceability Across Messages
Every payment carries a chain of IDs that allow full end-to-end tracing:
| ID | Who Sets It | Lives In | Purpose |
|---|---|---|---|
EndToEndId | Originating customer | pain.001 → pacs.008 → camt.054 | Customer's own reference; never changed |
InstrId | Debtor bank | pacs.008, pacs.002 | Bank's instruction reference |
TxId | Debtor bank | pacs.008, pacs.002 | Unique transaction ID for dedup |
MsgId | Each sender | All messages | Message-level dedup |
UETR | Debtor bank | SWIFT messages | Universal tracker for gpi |
AcctSvcrRef | Creditor bank | camt.053, camt.054 | Bank's ledger reference |
MndtId | Creditor/payer | Direct debit messages | PayTo/BECS mandate reference |
Payment Scheme Quick-Select
Is the payment a direct debit (pull)?
└─► PayTo (NPP) for new — BECS DDR for legacy
Is the payment international?
└─► SWIFT (MT103 / pacs.008)
Is the payment domestic?
├─ Same bank (both accounts at our institution)?
│ └─► On-Us — internal book transfer, no external network
│
├─ High-value or time-critical (> ~$250K)?
│ └─► RTGS / HVCS
│
├─ Bill payment with BPAY biller code?
│ └─► BPAY
│
├─ Creditor bank supports NPP?
│ └─► NPP / Osko — real-time, 24/7
│
└─ Fallback
└─► BECS Direct Entry — next business day
Risk & Compliance Checkpoints
Every payment — inbound or outbound — passes through these controls:
Payment Instruction
│
▼
┌──────────────────────────────────────────────────────┐
│ 1. DUPLICATE CHECK (TxId / EndToEndId) │
│ 2. SCHEMA VALIDATION (XSD / business rules) │
│ 3. AUTHENTICATION (customer / system auth) │
│ 4. SANCTIONS SCREENING (OFAC, UN, DFAT, AUSTRAC) │
│ 5. FRAUD ASSESSMENT (rules + ML model) │
│ 6. AML / TM CHECK (transaction monitoring) │
│ 7. BALANCE / LIMIT CHECK (outbound only) │
└──────────────────────────────────────────────────────┘
│
▼
Process Payment
Australian Regulatory Landscape
| Body | Role | Key Obligations |
|---|---|---|
| RBA | Central bank, settlement operator | ESA management, RTGS, NPP FSS |
| APRA | Prudential regulator | ADI licence, capital (Basel III), LCR/NSFR |
| AUSTRAC | AML/CTF regulator | TTR, IFTI, SMR reporting |
| ASIC | Market conduct regulator | Financial services licensing |
| OAIC | Privacy regulator | CDR / Open Banking data rules |
| AusPayNet | Payment scheme operator | BECS, cheque rules |
| NPPA | NPP operator | NPP/Osko/PayTo scheme rules |
Glossary of Common Terms
| Term | Definition |
|---|---|
| ADI | Authorised Deposit-taking Institution — licensed bank/credit union |
| ESA | Exchange Settlement Account — account at RBA used for final settlement |
| BIC / SWIFT code | Bank Identifier Code — uniquely identifies a financial institution |
| BSB | Bank State Branch — 6-digit code identifying an AU bank branch |
| IBAN | International Bank Account Number — standardised account number |
| PayID | Proxy address (phone/email/ABN) mapped to a BSB/account via NPP |
| UETR | Unique End-to-end Transaction Reference — UUID used in SWIFT gpi |
| DNS | Deferred Net Settlement — obligations netted and settled at end of day |
| RTGS | Real-Time Gross Settlement — each payment settled individually, in real time |
| LCR | Liquidity Coverage Ratio — APRA regulatory liquidity metric |
| PEP | Politically Exposed Person — requires enhanced due diligence |
| SAR / SMR | Suspicious Activity/Matter Report — filed with AUSTRAC |
| TTR | Threshold Transaction Report — cash transactions ≥ AUD 10,000 |
| IFTI | International Funds Transfer Instruction — all cross-border transfers |
| ChrgBr | Charge Bearer — who pays bank fees (DEBT/CRED/SHAR/SLEV) |
| Nostro | "Our" account held at another bank |
| Vostro | "Your" (another bank's) account held at our bank |
| Straight-Through Processing (STP) | Payment processed end-to-end without manual intervention |
| CoP | Confirmation of Payee — verifying payee name matches account before payment |
Java / Spring Stack Reference
Typical technology choices for a payment processing system:
| Layer | Technologies |
|---|---|
| API | Spring Boot, Spring Web MVC / WebFlux |
| Messaging | Spring Integration, Apache Kafka, IBM MQ, RabbitMQ |
| ISO 20022 Parsing | JAXB, prowide-core, open-banking-java-sdk |
| Database | PostgreSQL / Oracle (transactional), Redis (caching) |
| Security | Spring Security, HSM for key management |
| Scheduler | Spring Batch (batch payments), Quartz |
| Observability | Micrometer, Prometheus, Grafana, ELK Stack |
| Testing | JUnit 5, Mockito, Testcontainers, WireMock |
Contributing & Structure
Each page in this knowledge base follows a consistent structure:
- Overview — What it is and why it matters
- Key concepts — Definitions, types, tables
- Flow diagrams — ASCII art showing the process
- Field/code references — Lookup tables
- Java/Spring notes — Practical implementation snippets
- Related concepts — Cross-links to related pages