> ## Documentation Index > Fetch the complete documentation index at: https://docs.arcuserp.com/llms.txt > Use this file to discover all available pages before exploring further. # Retrieve a single order by UUID or order_number > Returns a single order (quote, sales order, invoice, or purchase order) by UUID or order_number. Shopify-style polymorphic path: pass either the UUID `id` field OR the human-readable `order_number` (e.g. `SO-001234`, `INV-0042`) as the `{id}` path segment. UUID lookup is direct; order_number lookup resolves within the entity scope (Layer 1). Supports `?expand[]=` for `line_items`, `customer`, `payments`, `fulfillments`, `returns`, and `timeline`. Returns 404 if no matching order belongs to the entity. Document type is indicated by the `document_type` field on the response object. Requires `orders:read` scope. ## OpenAPI ````yaml /openapi.yaml get /orders/{id} openapi: 3.1.0 info: title: Arcus ERP Public API version: 1.0.0 description: > Arcus ERP public REST API. Designed for external integrations and data migration. **Authentication.** Bearer token (API key) via the `Authorization` header. Format: `Authorization: Bearer ark_live_ent__` (or `ark_test_*` for sandbox). API keys are issued per-entity in **Settings > Developers > API Keys**. **Entity scoping.** The entity is encoded in the API key prefix; routes are flat (e.g. `/v1/accounts`, `/v1/orders`, `/v1/products`). A small set of platform endpoints (migration, reconciliation, events, webhook endpoints, API keys) use the `/v1/entities/{entity_id}/...` form -- those are noted in their tags. **Key capabilities.** - Related-resource hydration via `?expand[]=` (see `x-arcus-expand` on each resource). - Cursor-based pagination (`starting_after` / `ending_before` / `limit`). - Idempotency via the `Idempotency-Key` header. - Webhook events for asynchronous notification. - Conditional requests / ETag for cache validation. servers: - url: https://api.arcuserp.com/v1 description: Arcus ERP API (accepts both live `ark_live_*` and test `ark_test_*` keys) - url: https://dev-api.arcuserp.com/v1 description: >- Dev sandbox API (test-only data, accepts `ark_test_*` keys against dev RDS) security: [] paths: /orders/{id}: parameters: - name: id in: path required: true description: > The order's UUID `id` **or** its human-readable `order_number` (e.g. `SO-001234`, `INV-0042`, `Q-2026-0099`). UUID lookup uses a direct index and is slightly faster. order_number lookup resolves within the authenticated entity scope (Layer 1 enforced -- cross-entity collision impossible). schema: type: string examples: uuid: value: 550e8400-e29b-41d4-a716-446655440000 summary: UUID lookup (direct index) order_number: value: SO-001234 summary: order_number lookup (polymorphic) get: tags: - Orders summary: Retrieve a single order by UUID or order_number description: > Returns a single order (quote, sales order, invoice, or purchase order) by UUID or order_number. Shopify-style polymorphic path: pass either the UUID `id` field OR the human-readable `order_number` (e.g. `SO-001234`, `INV-0042`) as the `{id}` path segment. UUID lookup is direct; order_number lookup resolves within the entity scope (Layer 1). Supports `?expand[]=` for `line_items`, `customer`, `payments`, `fulfillments`, `returns`, and `timeline`. Returns 404 if no matching order belongs to the entity. Document type is indicated by the `document_type` field on the response object. Requires `orders:read` scope. operationId: getOrder parameters: - name: expand[] in: query description: > Hydrate related resources inline. Single-resource endpoints do NOT use the `data.` prefix (e.g. `expand[]=customer`). Valid paths: see `x-arcus-expand` below. schema: type: array items: type: string enum: - customer - account - line_items - line_items.product - payments - refunds - packages - fulfillments - gl_entries - invoice - tax_lines style: form explode: true responses: '200': description: Order object content: application/json: schema: $ref: '#/components/schemas/Order' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': $ref: '#/components/responses/Error' security: - ApiKeyAuth: [] components: schemas: Order: type: object description: > An Arcus ERP order document. One table holds quotes, sales_orders, invoices, returns, and purchase_orders -- always filter by document_type. entity_id is always from the API key (Layer 1 isolation). properties: id: type: string format: uuid object: type: string enum: - order entity_id: type: string format: uuid readOnly: true order_number: type: string readOnly: true document_type: type: string enum: - quote - sales_order - invoice - return - purchase_order order_status: type: string enum: - draft - confirmed - partially_fulfilled - fulfilled - cancelled - voided - awaiting_ach_clearance - on_hold payment_status: type: string enum: - unpaid - partially_paid - paid - overpaid - refunded - partially_refunded - voided fulfillment_status: type: string enum: - unfulfilled - partially_fulfilled - fulfilled account_id: type: string format: uuid nullable: true location_id: type: string format: uuid nullable: true po_number: type: string nullable: true order_date: type: string format: date-time nullable: true due_date: type: string format: date-time nullable: true subtotal: type: number discount_total: type: number shipping_total: type: number tax_total: type: number fee_total: type: number order_total: type: number list_price_total: type: number readOnly: true description: >- Derived (display-only): SUM(list_price * qty) over non-kit lines. The gross baseline of the gross-to-net bridge (List price minus pricing_savings equals subtotal). Never part of order_total. pricing_savings: type: number readOnly: true description: >- Derived (display-only): SUM(pricing_rule_adjustment * qty) over non-kit lines (positive magnitude). Per-unit pricing-rule savings already baked into subtotal via sell_rate (ASC 606 transaction price); shown as an informational List-to-Subtotal bridge, never subtracted from order_total. amount_paid: type: number readOnly: true description: 'SSOT: utils/ar-helpers.mjs::updateARBalance. Do not write directly.' balance_due: type: number readOnly: true tax_exempt: type: boolean delivery_option: type: string enum: - ship - pick_up - local_delivery notes: type: string nullable: true internal_notes: type: string nullable: true invoice_number: type: string nullable: true readOnly: true invoice_type: type: string enum: - order - manual - proforma - correction nullable: true is_on_hold: type: boolean readOnly: true hold_type: type: string nullable: true readOnly: true ship_complete: type: boolean source_platform: type: string nullable: true external_order_id: type: string nullable: true external_order_number: type: string nullable: true metadata: type: object nullable: true created_at: type: string format: date-time readOnly: true updated_at: type: string format: date-time readOnly: true ErrorEnvelope: type: object description: | Canonical error response envelope. All API errors use this shape. required: - error - code properties: error: type: string description: Machine-readable error key example: not_found code: type: string description: Machine-readable error code (often same as error) example: not_found type: type: string enum: - validation_error - permission_error - not_found - conflict - rate_limit - internal - expand_error - not_implemented example: not_found hint: type: string description: Human-readable one-sentence explanation (English) example: >- The requested order does not exist or does not belong to this entity. param: type: string description: The parameter that caused the error, if applicable example: expand[0] required: type: string description: The scope required (only on insufficient_scope errors) example: accounts:read request_id: type: string description: >- Unique request ID for support tracing (maps to CloudWatch log stream) example: req_abc123 responses: Error: description: Error response (400/401/403/404/409/422/429/500) content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' securitySchemes: ApiKeyAuth: type: http scheme: bearer description: | API key issued per entity via Settings > Developers > API Keys. Each key carries scopes (e.g. orders:read, products:write). Bearer token format: Authorization: Bearer ark_live_ent__ Test keys use ark_test_ent__. Both are issued per entity via Settings > Developers > API Keys. ````