---
title: "Update a Fax"
method: POST
path: "/Accounts/{AccountSid}/Faxes/{Sid}"
tags: ["Faxes"]
---

# Update a Fax

`POST /Accounts/{AccountSid}/Faxes/{Sid}`

Cancels a fax while it is still in `queued` status. Faxes that have begun processing, sending, or receiving cannot be canceled with this operation. Fax Logs are read-only and cannot change delivery state.

#### Permissions

The API token used to authenticate must have the following scope(s) enabled to make a successful request: _Fax_.

[Learn more about API scopes](/docs/platform/your-signalwire-api-space).

## Path parameters

- `AccountSid` string, uuid, required — Universal Unique Identifier.
- `Sid` string, uuid, required — Universal Unique Identifier.

## Response `200`

The request has succeeded.

- FaxResponse — Response containing a single fax.
  - `account_sid` string, required — The unique identifier for the account this fax is associated with.
  - `api_version` string, required — The version of the SignalWire API.
  - `date_created` string, required — The date and time, in ISO 8601 format, the fax was created.
  - `date_updated` string, required — The date and time, in ISO 8601 format, the fax was updated.
  - `direction` 'inbound' | 'outbound', required — Fax direction.
  - `from` string, required — The phone number, in E.164 format, the fax was sent from.
  - `media_url` string, nullable, required — The URL hosting the received media, or null if not available.
  - `media_sid` string, required — The unique identifier for the media instance associated with the fax instance.
  - `num_pages` string, nullable, required — The number of pages in the fax document, or null if not yet determined.
  - `price` string, nullable, required — The cost of the fax, or null if not yet calculated.
  - `price_unit` string, required — The currency, in ISO 4217 format, of the price.
  - `quality` 'standard' | 'fine' | 'superfine', required — Fax quality.
  - `sid` string, required — The unique identifier of the fax.
  - `status` 'queued' | 'processing' | 'sending' | 'delivered' | 'receiving' | 'received' | 'no-answer' | 'busy' | 'failed' | 'canceled', required — Fax status.
  - `to` string, required — The phone number, in E.164 format, the fax was sent to.
  - `duration` integer, required — The time, in seconds, it took to deliver a fax.
  - `links` FaxLinks, required — Fax links.
    - `media` string, required — Media associated with this fax.
  - `url` string, required — The URL of this resource.
  - `error_code` string, nullable, required — Error code for this resource, or null if no error.
  - `error_message` string, nullable, required — The description of this error, or null if no error.

## Other responses

- `400` — The request was invalid or cannot be processed. Check the error details for more information.
- `401` — Authentication failed. Please verify your credentials and try again.
- `404` — The requested resource was not found. Please verify the resource identifier.
- `422` — The request could not be processed due to validation errors. Check the error details for more information.

## Changes

- **2026-05-12** `5344c0c93a4c` — 1 breaking, 6 info
  - added 'unevaluatedProperties' constraint to the request body
  - added 'unevaluatedProperties' constraint to the response body for the status `200`
  - added 'unevaluatedProperties' constraint to the response body for the status `400`
  - added 'unevaluatedProperties' constraint to the response body for the status `401`
  - …3 more
- **2026-03-04** `2e516ba2383f` — 5 breaking
  - response property `error_code` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `error_message` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `media_url` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `num_pages` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - …1 more
- **2026-01-19** `d5fbaaddfa3e` — 16 breaking, 23 info
  - request body became required
  - the request property `Status` became required
  - removed the enum value `busy` of the request property `Status`
  - removed the enum value `delivered` of the request property `Status`
  - …35 more
- **2026-01-15** `a10b019314cd` — 1 info
  - request body became optional
- …earlier changes not shown

[Full history](https://skmtc.dev/signalwire/apis/compatibility-api/changes/Accounts/:AccountSid/Faxes/:Sid/post.md)

---

[API](https://skmtc.dev/signalwire/apis/compatibility-api.md) · [All operations](https://skmtc.dev/signalwire/apis/compatibility-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/signalwire/compatibility-api/revisions/723316346320/schema)