> ## 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. # Refund a return > Issues a refund against a received, inspected, restocked, written-off, sent-to-vendor, or closed return, optionally split across multiple original payment sources via `allocations[]`. Requires `returns:write` and `payments:write` scopes plus the `payments.refund_void` permission; calling it again with the same amount on the same return returns the cached result, and a different amount returns 409. A return whose refund accounting has put on hold with a question for the office is refused with 409 `refund_on_hold` until the office answers; nothing is refunded and no amount owed changes while it is held. ## OpenAPI ````yaml /openapi.yaml post /returns/{id}/refund 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. **Changelog.** Entries are dated and name every published contract whose MEANING moved, not only the ones whose field names changed. The narrative version of the same entries, written for integrators, is published at https://arcuserp.mintlify.app/changelog. **2026-09-22 (planned 2026-09-21), REORDER-BUYER-TRUTH: demand changed what it MEANS on three published contracts, with no field renamed.** An integrator that pins field names sees no breakage and different numbers, which is why this entry exists. - **Demand now counts build consumption.** `demand_avg_per_day` on the public product, kit and inventory-balance objects, and `daily_demand` / `demand_basis` / `net_suggested_qty` on `GET /v1/purchasing/reorder-report`, are composed from fulfilled sales lines PLUS posted `build_consume` inventory draws: each physical decrement of a product counts exactly once. The previous rule adopted an internal-consumption basis only when the sales blend was exactly zero, so a product both sold AND consumed into work orders planned as if the build draws did not exist. Products drawn into work orders move; on one production-shaped dataset five did, the largest from 0.05/day to 14.95/day. - **`demand_basis` now carries four values, not two:** `sales`, `sales_and_builds`, `builds` and `consumption`. A consumer with a two-branch reader (anything that is not `consumption` is `sales`) silently hides the two new ones. - **`current_demand_units` on `GET /v1/inventory/balances/:id` moved, by a second rule.** It counts committed-but-unshipped CUSTOMER demand, and it now counts a kit component's own line rather than its parent kit line, and excludes non-sales documents. On one production dataset 269 of 1,043 balance rows changed, 227 of them downward; the largest single move was 1,941 to 25, on a product whose open PURCHASE order line had been reported as customer demand. Re-baseline anything that alerts or reorders off this field. - `run_rate_30/90/180/365` and `blended_daily` on the same balance object move for the first reason above. - **Added, not changed:** `GET /v1/purchasing/reorder-report` accepts `demand_window` and returns the unit, cover-through and reorder-point-provenance fields documented on that operation; `order_multiple` is accepted and returned on the product-vendor doors. - **Volume note.** The `inventory.low_stock`, `inventory.out_of_stock` and `inventory.back_in_stock` webhook events are population-gated on `on_hand <= reorder_point`, and reorder points move with the demand above, so subscribers should expect a one-time step change in event volume around the release. 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: /returns/{id}/refund: parameters: - name: id in: path required: true schema: type: string format: uuid post: tags: - Returns summary: Refund a return description: >- Issues a refund against a received, inspected, restocked, written-off, sent-to-vendor, or closed return, optionally split across multiple original payment sources via `allocations[]`. Requires `returns:write` and `payments:write` scopes plus the `payments.refund_void` permission; calling it again with the same amount on the same return returns the cached result, and a different amount returns 409. A return whose refund accounting has put on hold with a question for the office is refused with 409 `refund_on_hold` until the office answers; nothing is refunded and no amount owed changes while it is held. operationId: refundReturn parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: content: application/json: schema: type: object properties: amount: type: number format: float description: >- Refund amount. Defaults to sum of return_items.refund_amount. When allocations[] is supplied, must equal SUM(allocations[].amount). payment_method: type: string enum: - original - store_credit - check - cash default: original description: >- Single-source path only. Ignored when allocations[] is supplied. allocations: type: array description: | Multi-source refund split. When present, the refund is executed per-payment across these order_payments rows (operator-picks). SUM(allocations[].amount) must equal the total refund within 1 cent. items: type: object required: - payment_id - amount properties: payment_id: type: string format: uuid description: An order_payments.id on the RMA's original order. amount: type: number format: float description: >- Dollars to refund against this payment source (must be > 0 and <= the source's remaining refundable amount). reason: type: string reason: type: string responses: '200': description: Refund issued content: application/json: schema: type: object properties: data: type: object properties: return_id: type: string format: uuid return_number: type: string amount: type: number payment_method_type: type: string description: '''multi_source'' when allocations[] was supplied.' order_refund_id: type: string format: uuid credit_memo_id: type: string format: uuid batch_id: type: string format: uuid description: >- Multi-source only: GL batch grouping all per-allocation journal entries. allocations: type: array description: 'Multi-source only: per-allocation result rows.' items: type: object properties: payment_id: type: string format: uuid source_method: type: string amount: type: number order_refund_id: type: string format: uuid refund_payment_id: type: string format: uuid status: type: string enum: - succeeded - already_processed idempotent: type: boolean '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': $ref: '#/components/responses/Error' '409': description: > The refund cannot be issued in the return's current state. `code` includes: - `refund_on_hold`: accounting put this return's refund on hold with a question for the office. Nothing is refunded until the office answers the question, which releases the hold. `meta.refund_hold` carries `return_id`, `return_number`, `note_id`, `held_by`, `held_by_name`, `held_at` and `question`. - `state_transition_invalid`: the return is not in a status a refund is allowed from. - `already_settled`: what is owed on this return is already settled, so more would refund the customer twice. - `refund_already_issued`: a refund of a different amount was already issued for this return. content: application/json: schema: allOf: - $ref: '#/components/schemas/ErrorEnvelope' - type: object properties: meta: type: object description: Present on `refund_on_hold`. properties: refund_hold: type: object properties: return_id: type: string format: uuid return_number: type: string note_id: type: string format: uuid nullable: true description: The note that holds the question. held_by: type: string format: uuid nullable: true held_by_name: type: string nullable: true held_at: type: string format: date-time nullable: true question: type: string nullable: true '422': $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. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.