# Faxing over SIP

Cloud Voice supports both sending and receiving faxes. Inbound faxing works by routing a phone number to the fax service; outbound faxes can be submitted programmatically through the [API](/sip/api/). Fax devices are managed through the fax service rather than as regular SIP trunks, and every transmission reports its progress through status events.

## Receiving faxes

Route a phone number to **fax** from the number's detail panel on the **Numbers** page in the [dashboard](https://voice.izt.cloud), the same panel where you set trunk, SIP URI, and other routing (see [Inbound Number Routing](/sip/routing/inbound/)). Calls to that number are then answered by the fax service and received as documents.

### Viewing received faxes

*Detailed steps coming soon.*

## Sending faxes

Outbound fax transmission is available through the API, you submit a document and a destination number, and the platform originates the fax call and reports the result. See the [API Reference](/sip/api/).

### Sending from the dashboard

*Detailed steps coming soon.*

## Transmission status

Fax transmissions are tracked end to end, including the negotiation with the far-end machine, and status updates are delivered as events, so your systems can know whether a fax succeeded, failed, or needs to be retried. See [Webhooks & Events](/sip/webhooks/).

## Reliability guidance

Fax is far less tolerant of network imperfections than voice: a moment of packet loss that a caller wouldn't notice can abort a fax page. To keep success rates high:

- **Use uncompressed audio codecs** (PCMU/PCMA) for any trunk path that carries fax, compressed codecs such as G729 corrupt fax tones.
- **Keep the network path stable**: jitter and packet loss are the leading causes of mid-page failures; prefer wired, uncongested links.
- **Prefer the platform fax service** over running fax through your own PBX audio path, the service handles the fax protocol directly and tracks negotiation results.
- **Watch the status events**: a failure report includes the stage at which the transmission failed, which tells you whether to blame the line, the far end, or the document.

:::note
Multi-page and high-resolution documents take proportionally longer and are more exposed to line quality; if a long fax fails repeatedly, try splitting it.
:::