Transaction Webhooks

The IIMMPACT platform sends webhook notifications when a transaction's status changes. To receive these notifications, configure a Callback URL — a secure HTTPS endpoint on your server that IIMMPACT will call with the transaction data.

Configure Your Callback URL

From the Developer > Webhooks page in the Dashboard:

1. Under Webhook Configuration, enter your callback URL.
2. Choose the HTTP method — POST or GET.
3. Click Save.

You can also configure the callback URL programmatically via the Set Callback URL API or retrieve your current settings via the Get Callback URL API.

Requirements

• Your endpoint must be publicly reachable.
• Use HTTPS for security.
• Return a 2xx response quickly to acknowledge receipt.

What Triggers a Callback?

IIMMPACT sends a callback when a transaction's status changes. The payload includes the current status — Processing, Succesful, or Failed — along with the full transaction details.

For the complete payload format and field descriptions, see Transaction Webhook Payload.

Security

Transaction callbacks do not currently include a cryptographic signature. Verify authenticity by allowlisting IIMMPACT callback IPs, matching the refid against your pending transactions, and optionally re-querying the transaction status. HMAC signature verification is planned.

Retry Behavior

If your endpoint fails to respond, IIMMPACT will retry the callback:

Setting	Value
Timeout	30 seconds per request
Retry limit	3 retries
Retry delay	60 seconds between attempts

What triggers a retry:

• HTTP 5xx (server errors)
• HTTP 429 (rate limited)
• HTTP 408 (timeout)
• Network errors (connection refused, DNS failure, timeout)

What does NOT retry:

• HTTP 4xx client errors (except 408/429) — these are treated as permanent failures

WARNING

If delivery fails, we retry up to 3 times with 60-second delays. You'll be notified via email/WhatsApp on the first failure (once per 24 hours). Failed callbacks are logged and monitored. Ensure your endpoint returns 2xx within 30 seconds to avoid delivery issues.

WARNING

If your server uses IP allowlisting, you must allowlist IIMMPACT's callback IPs. See Transaction Webhook Payload for the full list.