> ## 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. # Write off a vendor bill balance > **Authorization:** requires `purchasing:write` API-key scope AND the per-user `accounting.approve_bill` permission (SoD parity sweep 2026-05-16; income recognition is controller-tier authority). System-actor calls denied. Writes off the outstanding balance of a vendor bill as income recognition. **GAAP basis (FASB ASC 405-20):** writing off AP is a gain from extinguishment of liability -- NOT an expense. The journal entry posted is: ``` DR Accounts Payable (ap_account) CR Vendor Write-Off Income (4998) ``` **Distinction from `DELETE /vendor-bills/{id}` (void):** - Void reverses the original AP entry entirely and requires `amount_paid = 0`. - Write-off posts a **new** income-recognition JE and allows partial payments to remain. Only the remaining `balance_due` is written off. The bill's `status` transitions to `written_off` (terminal state). The original bill journal entry remains intact on the books. **Idempotency:** re-POST with the same `(source_type=WRITE_OFF, source_id=bill_id)` pair returns the cached result without re-posting the JE. **Period lock:** write-off of a bill in a locked tax year returns HTTP 422 `closed_period`. Requires `purchasing:write` scope. ## OpenAPI ````yaml /openapi.yaml post /vendor-bills/{id}/write-off 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: /vendor-bills/{id}/write-off: parameters: - name: id in: path required: true schema: type: string format: uuid - name: Idempotency-Key in: header required: false schema: type: string description: >- Optional idempotency key (UUID). Re-POST with same key returns cached 200 without re-processing. post: tags: - Purchasing summary: Write off a vendor bill balance description: > **Authorization:** requires `purchasing:write` API-key scope AND the per-user `accounting.approve_bill` permission (SoD parity sweep 2026-05-16; income recognition is controller-tier authority). System-actor calls denied. Writes off the outstanding balance of a vendor bill as income recognition. **GAAP basis (FASB ASC 405-20):** writing off AP is a gain from extinguishment of liability -- NOT an expense. The journal entry posted is: ``` DR Accounts Payable (ap_account) CR Vendor Write-Off Income (4998) ``` **Distinction from `DELETE /vendor-bills/{id}` (void):** - Void reverses the original AP entry entirely and requires `amount_paid = 0`. - Write-off posts a **new** income-recognition JE and allows partial payments to remain. Only the remaining `balance_due` is written off. The bill's `status` transitions to `written_off` (terminal state). The original bill journal entry remains intact on the books. **Idempotency:** re-POST with the same `(source_type=WRITE_OFF, source_id=bill_id)` pair returns the cached result without re-posting the JE. **Period lock:** write-off of a bill in a locked tax year returns HTTP 422 `closed_period`. Requires `purchasing:write` scope. operationId: writeOffAPBillV1 requestBody: required: true content: application/json: schema: type: object required: - reason properties: reason: type: string description: >- Human-readable reason for the write-off (e.g., "Vendor bankruptcy", "Negotiated settlement"). notes: type: string description: Optional additional context. idempotency_key: type: string format: uuid description: >- Optional idempotency key. Identical to Idempotency-Key header; body value takes precedence. example: reason: Vendor bankruptcy -- confirmed 2026-05-13 notes: Docket 24-11842, Western District of Louisiana responses: '200': description: Bill written off content: application/json: schema: type: object properties: data: type: object properties: success: type: boolean id: type: string format: uuid bill_number: type: string amount_written_off: type: number new_status: type: string enum: - written_off journal_entry_id: type: string format: uuid nullable: true '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': $ref: '#/components/responses/Error' '422': $ref: '#/components/responses/Error' '500': $ref: '#/components/responses/Error' security: - ApiKeyAuth: [] components: 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. ````