Cancel Order
Cancel a pending limit order.
Refunds reserved funds (BUY) or restores reserved shares (SELL). Only PENDING orders owned by the authenticated user can be cancelled.
Authorizations
Issue from /v1/keys (or admin-issued for enterprise tier).
Headers
Your PolySimulator API key
Polymarket-CLOB-compat alias for X-API-Key (underscore form). SDK clients ported from Polymarket can authenticate without changing header names. X-API-Key takes precedence when both are provided.
PM-CLOB-compat dashed-form alias for X-API-Key. Same value semantics as POLY_API_KEY but with HTTP-conventional dash separators. Both spellings are accepted end-to-end.
PM-CLOB-compat: Authorization: Bearer ps_live_... (or ps_test_...) is accepted as an alias for X-API-Key so py-clob-client and other ported SDKs authenticate without header name changes. Bearer JWTs are NOT accepted here — use the dashboard-auth endpoints for those.
Path Parameters
Response
Successful Response
Why a CANCELLED order was cancelled - a stable snake_case machine tag. An order cancelled inside the request that created it (a marketable IOC/FAK that could not fill) reports the no-fill cause, for example 'price_did_not_cross', 'fok_insufficient_depth', 'book_depleted', 'depth_required', 'no_live_price' or 'no_book_price'. An order cancelled while resting on the book reports for example 'gtd_expired', 'stale_market', 'stale_or_mismatched_book' or 'reset'. Null on non-cancelled statuses and on legacy rows, so branch on status to detect cancellation and on this field to learn the cause.