> For the complete documentation index, see [llms.txt](https://developer.convergegate.com/legacy/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.convergegate.com/legacy/card-server-to-server/notifications.md).

# Notifications

Notifications are sent with HTTP protocol to URL provided by merchant. Data is transmitted as POST parameter strdata, which contain XML structure.

{% hint style="info" %}
Notification / Webhook URL must be provided beforehand so that traffic can be allowed.
{% endhint %}

## Notifications

{% content-ref url="/pages/Utw9YDcUavQaEGuWwCKE" %}
[Notifications](/legacy/card-server-to-server/notifications.md)
{% endcontent-ref %}

## 850 – Transaction state Notification

{% content-ref url="/pages/eX50isIl13wbgk5J7J43" %}
[850 – Transaction state Notification](/legacy/card-server-to-server/notifications/850-transaction-state-notification.md)
{% endcontent-ref %}

## 860 – Refund Notification

{% content-ref url="/pages/yKiaqVBLiLQCcV7xTL7d" %}
[860 – Refund Notification](/legacy/card-server-to-server/notifications/860-refund-notification.md)
{% endcontent-ref %}

## 880 – Dispute Notification

{% content-ref url="/pages/pMcu33iAbYCKlZRfnS4W" %}
[880 – Dispute Notification](/legacy/card-server-to-server/notifications/880-dispute-notification.md)
{% endcontent-ref %}

{% hint style="info" %}
**Good to know:** Using the 'Page Link' block lets you link directly to a page. If this page's name, URL or parent location changes, the reference will be kept up to date. You can also mention a page – like [Authentication](/legacy/card-server-to-server/overview/authentication.md) – if you don't want a block-level link.
{% endhint %}