SEPA Instant Payment APIs
ImPAI API Architecture Overview​
ImPAI provides a comprehensive set of RESTful APIs that support the full lifecycle of SEPA Instant (SCT Inst) payments — from initiation and validation to operational handling, exception processing, and reporting.
These services are structured to provide:
- ✅ Modular and scalable integration
- ✅ End-to-end traceability across payment message flows
- ✅ Consistent data models and validation rules
- ✅ Seamless interoperability with core banking, clearing systems, and monitoring layers
Service Categories​
| Category | Purpose |
|---|---|
| Initiation Services | Create, update, or cancel payment instructions before processing. |
| R-Transaction Services | Handle recall, return, and resolution exception flows. |
| Inquiry Services | Track message lifecycle status and support investigations. |
| Validation Services | Perform data integrity and SEPA rule validation at multiple stages. |
| Backoffice Services | Ingest payment instructions from internal financial systems. |
| Data Retrieval Services | Provide detailed lookup for audit, reporting, and operational use. |
Each service category defines consistent API endpoints and follows standardized message formats to ensure reliable integration with external and internal systems.
Where Each API Fits in the SCT Inst Lifecycle​
SCT Inst processing involves several coordinated steps, and each API in ImPAI is designed to support a specific part of this lifecycle. The diagram below provides a high-level overview of where each service fits — from the initial payment initiation through validation, settlement, inquiries, and exception handling. Use it as a guide to understand how the different API categories interact within the full processing journey.
| Legend | |
| Light Blue | API groups that perform a specific functional role in SCT Inst |
| Underlined Blue | Clickable — opens thecorresponding API documentation section |
| Light Green | Core execution stage that interacts with clearing & settlement systems |
Supported Message Types​
ImPAI supports all SEPA Instant Payment message types required by the EPC SCT Inst Rulebook.
Messages are exchanged using ISO 20022 formats and extended internally with additional metadata for processing and traceability.
| Message Type | Full ISO Name | Purpose in SCT Inst |
|---|---|---|
| pain.001.001.09 | Customer Credit Transfer Initiation | Customer (debtor) instructs a payment to their bank. |
| pain.002.001.10 | Customer Payment Status Report | Status update from bank to customer system (e.g., accepted or rejected). |
| pacs.002.001.10 | FI Payment Status Report | Status feedback between banks or from clearing system. |
| pacs.004.001.09 | Payment Return | Return of funds when a credit transfer cannot be completed. |
| pacs.008.001.08 | Financial Institution Credit Transfer | Actual credit transfer between banks via the clearing system. |
| pacs.028.001.03 | FI Payment Status Request (Inquiry) | Request for payment status or investigation case. |
| camt.029.001.09 | Resolution of Investigation | Response to inquiry or recall — final or interim resolution. |
| camt.056.001.08 | FI Payment Cancellation Request (Recall) | Request to cancel a previously sent transaction. |
These message types cover all operational flows:
✅ Standard credit transfers
✅ Exception handling (Recalls, Returns, Inquiries)
✅ Status visibility for customers and between banks
List of Available Endpoints​
| Method | Endpoint | Description | Use Cases |
|---|---|---|---|
| POST | /api/sct-inst/v1/ | Initiates a SEPA Instant payment from a PAIN.001. Returns identifier if successfully authorised. | SEPA Instant Payment Initiation |
| POST | /api/sct-inst/v1/ | Validate the fields in a filled Payment Instruction (pain.001) message. | SEPA Instant Payment Initiation |
| POST | /api/sct-inst/v1/ | Prepares and generates a SEPA Instant recall request. Returns a Cancellation ID on success. | SEPA Instant Payment Recall |
| POST | /api/sct-inst/v1/ | Returns funds for a SEPA Instant recall request. Returns Return ID on success. | SEPA Instant Return of Funds |
| POST | /api/sct-inst/v1/ | Processes a Resolution (negative response) to a SEPA Instant recall request. Returns Resolution ID. | SEPA Instant Recall Resolution |
| POST | /api/sct-inst/v1/ | Approve or reject payment instructions that are pending approval. Returns Transaction ID on success. | SEPA Instant Instruction approval |
| POST | /api/sct-inst/v1/ | Approve or reject returns that are pending approval. Returns Transaction ID on success. | SEPA Instant Return approval |
| POST | /api/sct-inst/v1/ | Approve or reject recalls that are pending approval. Returns Transaction ID on success. | SEPA Instant Recall approval |
| POST | /api/sct-inst/v1/ | Approve or reject resolutions that are pending approval. Returns Transaction ID on success. | SEPA Instant Resolution approval |
Message Structure in ImPAI APIs​
ImPAI adopts a unified internal JSON message model to ensure consistent communication across all microservices. This structure standardizes how payments are processed, routed, audited, and monitored throughout the system.
Each message contains the following core components:
| Component | Description |
|---|---|
| Common Metadata | Identifiers, timestamps, system of origin, message type, and lifecycle context. Enables full traceability and audit compliance. |
| Routing Information | Internal addressing details such as processing queues, target services, and flow control indicators. |
| Processing State | Current execution status including intermediate stages, retry counters, timestamps, and error diagnostics. |
| Data Payload | The business transaction content based on ISO 20022 message structures (e.g., pacs.008, camt.056), enriched with internal fields where required. |
Although the external API uses standardized request/response models, ImPAI converts them into this internal normalized format to maintain stability and extensibility across services.