- Overview
- Register the Callback URL in NMI
- Subscribe to eCheck ACH Transaction Events
- ACH Processing Timeline
- Troubleshooting
- Summary
This article explains how to configure the Network Merchants Inc. NMI webhook integration for eCheck ACH payment events. After completing these steps, NMI will send real-time transaction notifications to your configured callback URL when ACH capture events succeed or fail.
Register the Callback URL in NMI
Use the NMI Merchant Portal to register the webhook endpoint that will receive ACH payment event notifications.
- Log in to the NMI Merchant Portal:
https://secure.nmi.com/merchants/login.php - Enter your gateway admin credentials.
- In the left navigation menu, go to Settings > Transaction Options > Webhooks.
- Click Create or Add Webhook, depending on the option displayed in your NMI portal.
-
In the URL field, enter your HTTPS callback URL:
https://{your-domain}/Store/Integration/NMI/WebhookHandler.ashx - Confirm that the URL uses HTTPS and is publicly accessible by NMI.
Note: Replace {your-domain} with the domain used by your store or application environment.
Subscribe to eCheck ACH Transaction Events
After creating the webhook endpoint, select the transaction events that should trigger notifications for eCheck ACH payment processing.
| Event Type | Meaning |
|---|---|
transaction.capture.success |
ACH funds were captured or settled successfully. |
transaction.capture.failure |
ACH funds failed to capture or were returned. |
- In the webhook configuration page, locate the Event Type or Events section.
- Select transaction.capture.success.
- Select transaction.capture.failure.
- Click Save to activate the webhook endpoint.
Note: The webhook must be saved before NMI can begin sending transaction event notifications to the callback URL.
ACH Processing Timeline
ACH payments do not always complete immediately. Capture and settlement results may be delayed while the ACH transaction is processed.
- ACH capture may take 1–3 business days.
- A successful authorization does not always mean the ACH funds have fully settled.
- Use the webhook events to track final capture or return status.
Important: Do not treat an ACH payment as fully captured until the system receives a transaction.capture.success event or the transaction status is otherwise confirmed in NMI.
Troubleshooting
| Issue | Recommended Action |
|---|---|
| No webhook notifications are received. | Confirm the webhook endpoint was saved in Settings > Transaction Options > Webhooks and that the callback URL is publicly reachable over HTTPS. |
| ACH transactions appear delayed. | Allow 1–3 business days for ACH capture or return events to process. |
| Only some events are received. | Verify that both transaction.capture.success and transaction.capture.failure are selected for the webhook endpoint. |
| The webhook handler is not triggered. | Confirm the configured URL matches the required endpoint format: https://{your-domain}/Store/Integration/NMI/WebhookHandler.ashx. |
Summary
To enable NMI eCheck ACH webhook notifications, log in to the NMI Merchant Portal, open Settings > Transaction Options > Webhooks, create a webhook endpoint, and enter the callback URL:
https://{your-domain}/Store/Integration/NMI/WebhookHandler.ashxSubscribe to transaction.capture.success and transaction.capture.failure so the system can track successful ACH captures and failed or returned ACH transactions. ACH capture may take 1–3 business days, so webhook events should be used to confirm the final payment status.