eCheck & ACH Gateway Development

I am building a bespoke payment processing system and need the core module that can accept both eChecks and ACH transactions seamlessly. The workflow must cover customer authorization, bank verification, and settlement within US banking rails.

Alongside basic charge and settle flows, the gateway has to support two key features from day one: recurring billing cycles that I can configure by amount and interval, and real-time instant payment notifications so my application can update order status the moment a transaction changes state. Clear, well-documented webhooks or callback URLs will be fine for those notifications.

Code quality and clarity are important because this module will plug into an existing SaaS platform. Please structure it as a self-contained REST API (language is flexible; Node.js, PHP, Python or similar are all acceptable) with straightforward endpoints for create-customer, create-payment-method, charge, refund, and query. I will handle UI on my side, so focus entirely on back-end logic, bank integration, and response formatting.

Deliverables:
• Source code in a private Git repository
• Postman collection or equivalent for quick endpoint testing
• README that covers setup, environment variables, and example calls
• Brief hand-off session or screencast walking through recurring schedule configuration and webhook testing

The job is complete once I can run the service locally, trigger a test eCheck or ACH payment, see a recurring charge fire on schedule, and receive the corresponding instant notification payload.