---
search:
  tags:
    - Orders
    - POST
seo:
  description: >-
    Amends a resting order in place, changing its price and/or quantity. Side
    and… Reference for the POST /orders/{order_id}/amend endpoint in the REST
    API API.
sidebar:
  badge: POST
  label: Amend an Order
title: Amend an Order
type: openapi-operation
---
Amends a resting order in place, changing its price and/or quantity. Side and time in force are unchanged. Queue priority is preserved only when quantity strictly decreases at an unchanged price.

### Endpoint

- Method and path: `POST /orders/{order_id}/amend`
- Operation ID: `amendOrder`
- API reference: [POST /orders/{order_id}/amend](/api-reference/orders/amendorder)

#### Authorization

- Accepted credentials: `UDX-Access-Key` header and `UDX-Access-Timestamp` header and `UDX-Access-Signature` header; or Bearer token in `Authorization`
- Details: [Authentication](/authentication)

#### Parameters

- `UDX-Version` (`header`) — Dated API version (YYYY-MM-DD). Omit to use the oldest supported version. An unknown version returns `400`.
- `UDX-Idempotency-Key` (`header`) — Optional client-generated key that makes a mutation safe to retry. Reuse it only for a byte-identical retry. When present, it is included in the request signature; omitting it disables UDX idempotency for that request.
- `order_id` (`path`, required) — Exchange-assigned order identifier.

#### Request body

- Content type: `application/json`
- Schema: `AmendOrderRequest`
- Required: yes
- Fields:
  - `ticker` (Ticker, required)
  - `quantity` (required) — New total order quantity, in contracts (absolute, not a delta). Must exceed the quantity already filled.
  - `price` (required) — New limit price in YES price space, in dollars.
  - `client_order_id` — The existing order's client_order_id, for the caller's reference (the order is identified by the order_id path parameter).
  - `updated_client_order_id` — New correlation id for the amended order. The order keeps its existing client_order_id when omitted.

#### Responses

- `200` — The amended order.
- `400` — The request doesn't conform to this spec.
- `401` — No valid credential was provided.
- `404` — The requested resource doesn't exist or isn't visible to the caller.
- `409` — This key is still in use or its response cannot be replayed. The mutation may have run; check `detail` before retrying.
- `422` — This key belongs to a different request.
- `429` — The Member's request rate is exhausted. Wait for `Retry-After`.
- `500` — Something went wrong on UDX's side.
- `503` — Request admission is unavailable. Retry later.