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Payment API Integration

Let corporate treasury systems initiate payments directly, safely and in real time

This project builds a payment initiation API for the corporate banking channel, so that treasury teams can send payments from their own systems instead of typing each instruction into internet banking. A corporate customer submits a payment of 25,000 dollars to a supplier in New York, a payment of 100,000 euros to a supplier in Frankfurt, and a bulk file of 200 salary payments, all through the same API, and receives a real time response with the payment status. The business analyst defines the business problem, writes the requirements for initiation, validation, approval, screening and status reporting, designs the idempotency and error handling rules, and specifies the API contract that corporate customers build against. The project covers OAuth 2.0 authentication, daily limits, approval workflows, webhook notifications, sandbox testing and a controlled production launch with the first corporate customers.

Phases

Discovery and Business Case

Requirements and API Design

Architecture and Integration Design

Build Support

Testing and Certification

Launch and Hypercare

Deliverables

BRD

The Business Requirements Document states what the business needs from a payment initiation API for the corporate banking channel, including the payment types, currencies, channels and customer segments in scope. It covers single and bulk payment initiation, payment status enquiry, cancellation and webhook notifications, and it defines the business rules for limits, cutoffs, approval workflows, charges and exception handling. It is signed off by business, operations, compliance and technology before design starts.

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FSD

The Functional Specification Document describes how the payment initiation API must behave at each step, from request receipt and authentication through validation, limit checks, screening, routing and status reporting. It defines the rules for idempotency, duplicate prevention, timeout handling, retries and error reporting, and it states the behaviour for approvals, rejections and cancellations. Developers and testers use it as the precise specification for build and test.

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Process Flow

The Process Flow shows the end to end journey of a payment initiated through the API, from the corporate treasury system to beneficiary credit, with swimlanes for the customer, the API gateway, the payment hub, compliance and the clearing system. It shows decision points for authentication, validation, approval, screening and routing, and the exception paths for rejection, timeout and duplicate detection. Operations and integration teams use it to understand the new process and to train staff.

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Solution Architecture

The Solution Architecture describes the technology design for the payment API, including the API gateway, the authentication service, the payment orchestration service, the payment hub, the screening platform and the core banking system. It shows how requests flow between systems, where idempotency keys and correlation IDs are stored, how resilience and failover work, and how the design meets security, performance and audit requirements. It guides developers and infrastructure teams during build and deployment.

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Data Mapping Sheet

The Data Mapping Sheet lists every field that flows through the API, from the corporate request payload to the payment hub record, the clearing message and the ledger entry. It shows the source, the target, the data type, the transformation rule and the validation rule for each field, including party, account, amount, currency, value date, remittance information and charges. It is the reference that developers and testers use to build and verify every interface.

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API Specification

The API Specification defines the interfaces for payment initiation, payment status, payment cancellation, bulk file submission and webhook notifications. It lists each endpoint, the request and response payloads, the authentication method using OAuth 2.0, the error codes, the idempotency key handling, the correlation ID rules and the service levels for response time and availability. It lets corporate customers and channel teams integrate with the bank safely and consistently.

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Jira User Stories

Jira User Stories break the API build into small, deliverable pieces that a development team can complete in a sprint. Each story states the user need, the business value and the acceptance criteria, and it is linked to the BRD, the FSD and the data mapping sheet. Stories cover authentication, initiation, validation, approval, screening, status reporting, cancellation and webhooks, with clear priorities, dependencies and a definition of done.

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Acceptance Criteria

Acceptance Criteria define the conditions that must be met before an API feature or release is accepted by the business. Each criterion is specific, measurable and testable, and it states the expected result for a given request, including authentication, validation, approval, idempotency, status reporting and error handling. Criteria are agreed before development starts and are used as the basis for user acceptance testing, performance testing and production sign off.

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UAT Scenarios

UAT Scenarios describe the business tests that prove the API works end to end, from a 25,000 dollar payment initiated by a corporate treasury system to a 100,000 euro bulk file and a cancelled payment. Each scenario states the precondition, the test steps, the input request, the expected output and the evidence required. Scenarios cover a standard single payment, a payment above the approval threshold, a duplicate submission, an invalid IBAN, a timeout, a cancellation and a webhook delivery, so the business can sign off with confidence.

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RTM

The Requirements Traceability Matrix links every API requirement in the BRD to its functional specification, its design component, its user story, its test case and its UAT result. It shows which requirements are covered, which are in progress and which have failed testing, so that no requirement is lost during the build. It is the main evidence that the API meets the agreed scope and is ready for production release.

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