> ## 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. # Update header-level fields on a draft or submitted transfer > Updates a constrained set of header fields on a transfer in `draft` or `submitted` status. Allowed fields: `notes`, `expected_ship_date`, `expected_receive_date`, `carrier`, `tracking_number`, `transfer_notes`. Any other field returns 400 `field_not_writable`. Status guard: returns 409 `state_transition_invalid` when the transfer is in any status beyond `draft` or `submitted` (in_transit / shipped / receiving / closed / cancelled are immutable at the header level). Item-level mutations are not supported on PATCH; cancel the transfer and create a new one to change items. Requires `inventory:write` scope. Idempotent via `Idempotency-Key`. ## OpenAPI ````yaml /openapi.yaml patch /transfers/{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: /transfers/{id}: parameters: - name: id in: path required: true schema: type: string format: uuid patch: tags: - Inventory summary: Update header-level fields on a draft or submitted transfer description: | Updates a constrained set of header fields on a transfer in `draft` or `submitted` status. Allowed fields: `notes`, `expected_ship_date`, `expected_receive_date`, `carrier`, `tracking_number`, `transfer_notes`. Any other field returns 400 `field_not_writable`. Status guard: returns 409 `state_transition_invalid` when the transfer is in any status beyond `draft` or `submitted` (in_transit / shipped / receiving / closed / cancelled are immutable at the header level). Item-level mutations are not supported on PATCH; cancel the transfer and create a new one to change items. Requires `inventory:write` scope. Idempotent via `Idempotency-Key`. operationId: updateTransferV1 parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: type: object properties: notes: type: string expected_ship_date: type: string format: date nullable: true expected_receive_date: type: string format: date nullable: true carrier: type: string nullable: true tracking_number: type: string nullable: true transfer_notes: type: string nullable: true responses: '200': description: Updated transfer header row content: application/json: schema: type: object properties: data: type: object '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': $ref: '#/components/responses/Error' '409': $ref: '#/components/responses/Error' security: - ApiKeyAuth: [] components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false description: | Client-generated unique key for idempotent POST/PATCH/DELETE operations. Alias for the Idempotency parameter. Max 255 chars. On retry with the same key, the original response is returned without re-executing the operation. Keys expire after 24 hours. schema: type: string maxLength: 255 responses: Error: description: Error response (400/401/403/404/409/422/429/500) content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' schemas: 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 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. ````