---
title: "SIP Refer a call"
method: POST
path: "/calls/{call_control_id}/actions/refer"
tags: ["Call Commands"]
---

# SIP Refer a call

`POST /calls/{call_control_id}/actions/refer`

Initiate a SIP Refer on a Call Control call. You can initiate a SIP Refer at any point in the duration of a call.

**Expected Webhooks:**

- `call.refer.started`
- `call.refer.completed`
- `call.refer.failed`

## Path parameters

- `call_control_id` string, required

## Request body

- ReferRequest
  - `sip_address` string, required — The SIP URI to which the call will be referred to.
  - `client_state` string — Use this field to add state to every subsequent webhook. It must be a valid Base-64 encoded string.
  - `command_id` string — Use this field to avoid execution of duplicate commands. Telnyx will ignore subsequent commands with the same `command_id` as one that has already been executed.
  - `custom_headers` CustomSipHeader[] — Custom headers to be added to the SIP INVITE.
    - `name` string, required — The name of the header to add.
    - `value` string, required — The value of the header.
  - `sip_auth_username` string — SIP Authentication username used for SIP challenges.
  - `sip_auth_password` string — SIP Authentication password used for SIP challenges.
  - `sip_headers` SipHeader[] — SIP headers to be added to the request. Currently only User-to-User header is supported.
    - `name` 'User-to-User', required — The name of the header to add.
    - `value` string, required — The value of the header.

## Response `200`

Successful response upon making a call control command.

- object
  - `data` CallControlCommandResult
    - `result` string

## Other responses

- `422` — Unprocessable entity. The request was well-formed but could not be processed due to semantic errors. This includes validation errors, invalid parameter values, call state errors, conference errors, queue errors, recording/transcription errors, and business logic violations.
- `default` — Unexpected error

---

[API](https://skmtc.net/team-telnyx/apis/telnyx-api.md) · [All operations](https://skmtc.net/team-telnyx/apis/telnyx-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/team-telnyx/telnyx-api/revisions/e32d46c5945b/schema)