> ## Documentation Index > Fetch the complete documentation index at: https://docs.predictamarkets.com/llms.txt > Use this file to discover all available pages before exploring further. # Cancel an Order > Cancels an open or partially-filled order and releases held balance. Cannot cancel a fully-filled order. ## OpenAPI ````yaml PUT /v1/markets/{market_id}/orders/{order_id}/cancel openapi: 3.0.3 info: title: Predicta Markets API description: >- The Predicta Markets REST API lets you build on top of a continuous double-auction prediction market platform. Users buy and sell shares in YES/NO outcomes of real-world events. When a market resolves, holders of the winning side receive payouts; holders of the losing side lose their stake. Data model hierarchy: Market → MarketAsset → MarketAssetOption (prediction key) → Order. A Market is a question about a real-world event (e.g. 'Will Arsenal win the Premier League?'). Each Market contains one or more MarketAssets — the tradeable outcomes. Simple binary markets have a single asset; multi-player markets (e.g. Player of the Match) have one asset per candidate. Each MarketAsset exposes two options, YES and NO, each carrying a prediction_key — the unique hash you pass when placing an order to identify exactly which outcome you are trading. Trading flow: (1) call GET /v1/markets to find a market; (2) inspect market_assets and their options to get the prediction_key for the outcome you want; (3) call POST /v1/markets/{market_id}/orders with that prediction_key, your price, and quantity. Orders match immediately when a counterparty exists, otherwise they rest as open limit orders in the order book. Price system: all prices are integers in the range 1–99, representing cents. Price equals implied probability in percent — a YES price of 65 means the market implies a 65% chance the event will occur. YES and NO prices for the same asset always sum to approximately 100. Currency: the platform's internal unit is PT (Predicta Token). Balances, prices, and payout amounts are expressed in PT unless the market was created with a real-currency denomination. QID system: many resources expose a human-readable qualified ID (qid) alongside the numeric id. QIDs are computed, not stored as database columns. Prefix conventions — MA: market, MAA: market asset, AP: account payout. Most path parameters accept either the numeric id or the qid interchangeably. Authentication: include your API key in the X-Api-Key request header. All account-scoped endpoints require authentication. Market listing and detail endpoints are public. version: 1.0.0 contact: email: api-support@predictamarkets.com servers: - url: https://api.predictamarkets.com description: Production security: [] paths: /v1/markets/{market_id}/orders/{order_id}/cancel: put: tags: - Market summary: Cancel an Order description: >- Cancels an open or partially-filled order and releases held balance. Cannot cancel a fully-filled order. operationId: cancel_market_order_v1_markets__market_id__orders__order_id__cancel_put parameters: - name: market_id in: path required: true schema: $ref: '#/components/schemas/TQID' - name: order_id in: path required: true schema: type: integer title: Order Id description: Integer ID of the order to cancel responses: '200': description: Order cancelled content: application/json: schema: type: string title: >- Response Cancel Market Order V1 Markets Market Id Orders Order Id Cancel Put example: id: 501 market_id: 12 market_asset_id: 34 account_id: 1042 order_type: BUY opinion_side: 'YES' price: '65.00' quantity: '10.00' initial_quantity: '10.00' status: CANCELLED prediction_key: mkt-12-yes auto_cancel_at: null created_at: '2025-04-10T09:00:00Z' updated_at: '2025-04-10T09:01:00Z' '400': description: Bad request content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: detail: Order is already filled and cannot be cancelled '401': description: Not authenticated content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: detail: Not authenticated '403': description: Forbidden content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: detail: You are not authorized to cancel this order '404': description: Not found content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: detail: Order not found '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' '500': $ref: '#/components/responses/InternalServerError' security: - apiKey: [] components: schemas: TQID: anyOf: - type: string - type: integer description: >- Flexible identifier type that accepts either a numeric integer ID or a human-readable qualified ID string (QID). QIDs follow a prefix convention: MA for markets, MAA for market assets, AP for account payouts. Most path parameters that accept an ID use this type so callers can use whichever form is more convenient. ErrorResponse: type: object properties: detail: type: string description: Human-readable error message required: - detail title: ErrorResponse HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError description: >- Returned by FastAPI when request validation fails (HTTP 422). Contains one or more ValidationError entries describing each invalid field. ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location description: >- Path to the invalid field as a list of keys and/or array indices. For example, ['body', 'price'] indicates the price field in the request body failed validation. msg: type: string title: Message description: Human-readable explanation of what validation rule was violated. type: type: string title: Error Type description: >- Machine-readable Pydantic error type (e.g. 'value_error.missing', 'type_error.integer'). type: object required: - loc - msg - type title: ValidationError description: >- A single field validation failure within an HTTP 422 response. The loc array traces the path to the invalid field (e.g. ['body', 'price']). responses: InternalServerError: description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: detail: An unexpected error occurred. Please try again later. securitySchemes: apiKey: type: apiKey in: header name: X-Api-Key x-default: your-api-key-here ````