> ## 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. # Apply a vendor credit to a vendor bill > Applies an open vendor credit to a single vendor bill, reducing the outstanding AP balance. The applied amount is clamped to `min(amount, vendor_credit.remaining_amount)`. Effects: - Inserts a `vendor_credit_applications` row (per-bill audit trail). - Updates `vendor_credits.remaining_amount` and `status` (`applied` / `partially_applied`). - Reduces `vendor_bills.balance_due` via the canonical SSOT writer (`updateAPBalance`). - Emits `activity_log` row (`credit_applied`) + `vendor_credit.applied` broadcast. - GL: at apply time, NO new journal entry is posted; the AP-reducing JE was already posted at credit issuance. The `vendor_credit_applications` row links back to the issuance JE (NetSuite / QuickBooks / Acumatica parity: Apply Vendor Credit posts no duplicate GL). Requires `purchasing:write` scope + per-user `accounting.post` permission (SoD; the same gate the native AP UI uses). Idempotency: send `Idempotency-Key` header to make retries safe; replays return the original result without re-applying. ## OpenAPI ````yaml /openapi.yaml post /vendor-credits/{id}/apply 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-credits/{id}/apply: parameters: - name: id in: path required: true schema: type: string format: uuid post: tags: - Purchasing summary: Apply a vendor credit to a vendor bill description: > Applies an open vendor credit to a single vendor bill, reducing the outstanding AP balance. The applied amount is clamped to `min(amount, vendor_credit.remaining_amount)`. Effects: - Inserts a `vendor_credit_applications` row (per-bill audit trail). - Updates `vendor_credits.remaining_amount` and `status` (`applied` / `partially_applied`). - Reduces `vendor_bills.balance_due` via the canonical SSOT writer (`updateAPBalance`). - Emits `activity_log` row (`credit_applied`) + `vendor_credit.applied` broadcast. - GL: at apply time, NO new journal entry is posted; the AP-reducing JE was already posted at credit issuance. The `vendor_credit_applications` row links back to the issuance JE (NetSuite / QuickBooks / Acumatica parity: Apply Vendor Credit posts no duplicate GL). Requires `purchasing:write` scope + per-user `accounting.post` permission (SoD; the same gate the native AP UI uses). Idempotency: send `Idempotency-Key` header to make retries safe; replays return the original result without re-applying. operationId: applyVendorCreditV1 requestBody: required: true content: application/json: schema: type: object required: - vendor_bill_id - amount properties: vendor_bill_id: type: string format: uuid description: >- Open vendor bill to apply the credit against (must belong to the same vendor as the credit). amount: type: number exclusiveMinimum: 0 description: Amount to apply; clamped to credit's remaining_amount. responses: '200': description: Vendor credit applied successfully content: application/json: schema: type: object properties: data: type: object properties: success: type: boolean enum: - true applied_amount: type: number description: Actual amount applied (clamped to remaining_amount) remaining_amount: type: number description: >- New remaining balance on the credit after this application status: type: string enum: - applied - partially_applied description: New status of the vendor credit application_id: type: string format: uuid description: vendor_credit_applications row id (audit trail) '400': description: >- Missing `vendor_bill_id`, non-positive `amount`, no remaining credit, or vendor mismatch content: application/json: schema: type: object properties: error: type: string '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' '404': description: Vendor credit or vendor bill not found (entity-scoped) content: application/json: schema: type: object properties: error: type: string '422': description: >- Vendor credit not applicable (applied / voided / expired / zero-balance / past-expiry) content: application/json: schema: type: object properties: error: type: string description: '`vendor_credit_not_applicable` or specific code' message: type: string credit_id: type: string format: uuid reason: type: string nullable: true 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. ````