> For the complete documentation index, see [llms.txt](https://support.trybit.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.trybit.com/integration/postback.md).
# Payment Notifications (POSTBACK)
POSTBACK: configuration, authenticity verification, and notification history for payment status.
**POSTBACK** is a notification that Trybit sends to the URL specified by the merchant (Notification URL / callback URL) whenever an invoice's status changes. This is the primary way to learn about a payment automatically, without manually polling the API.
### How to configure It
The Notification URL is specified in the project's integration settings — in the "Notification URL" field (available only in test mode, see [Project Settings](/getting-started/project-settings.md)).
### How It works
1. An invoice is created — manually, via API, or through any other integration method.
2. The customer pays the invoice.
3. Trybit sends a POSTBACK to the project's Notification URL — with invoice data: status, invoice number (INV), payment amount and currency, and your internal order\_id (if it was passed when creating the invoice).
4. Additionally, invoice status can be checked at any time via the API by invoice number (INV) — the invoice-information method lets you request up to 100 invoices in a single call.
### How to verify a notification's authenticity
Every POSTBACK contains a signed token (JWT, HS256 algorithm) valid for **5 minutes** from the time it's sent. On the merchant's side, you need to verify this token using your project's Secret key — this confirms that the notification genuinely came from Trybit and wasn't forged.
One common cause of webhook-related issues is a time mismatch on the merchant's server: if the server clock is more than a few minutes off, the token falls outside the 5-minute window and is considered invalid. This is the first thing to check when troubleshooting missing postbacks.
### POSTBACK history
Your personal dashboard has a "Postback History" section — here you can see whether a postback was delivered successfully, and resend it if needed (including for invoices that were paid during test mode, even after exiting it).
{% hint style="success" %}
If you have any questions or need help, you can contact our support via chat on the website and in your personal account, as well as reach us on Telegram. Support contacts are listed [on our website](https://trybit.com/support).
{% endhint %}
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