> ## 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. # Reverse a vendor prepayment application > Takes one application of a vendor prepayment back off its bill: the application's journal entry is reversed (dated `effective_date` in an open period, else the entity's calendar day), the application is removed, and the bill's paid amount and balance due and the prepayment's balance are restored. The payment holds follow the state the reversal leaves (`holds_plan`): the bill and every other bill of the vendor on the prepayment's purchase order that has money to pay and to which open prepayment money is proposed again, and that no waiver names, is held again (`payment_hold` for this bill, `restored_bill_holds` for the others), whatever write had released it (the hold a system release took off comes back when its text still names exactly the open money, else a fresh hold names it); a person's `unrelieved_prepayment` hold that a full relief ended comes back on this bill, a hold a person released stays released for the prepayments it waived, and a paid or voided bill is never held again. Requires `ap:write` scope, and the call is refused 404 `prepayment_application_not_found`, or 409 `bill_header_unapply_unsupported` (nothing written) where the AP balance writer cannot yet give the amount back. ## OpenAPI ````yaml /openapi.yaml post /vendor-prepayments/{id}/unapply 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. **October 2026: the order status values are the ones the API sends.** The `Order` schema's `order_status`, `payment_status`, `fulfillment_status` and `document_type` now list the values the order endpoints actually return (`order_status`: draft, open, processing, fulfilled, cancelled, archived, expired, awaiting_ach_clearance; `payment_status`: unpaid, partial, processing, paid, refunded, terms, overdue, overpaid, partially_refunded; `fulfillment_status`: unfulfilled, partial, fulfilled, backordered, awaiting_pickup; `document_type` adds late_fee_invoice). The values themselves did not change; the schema had listed names the API never sends (`confirmed`, `partially_paid`, `partially_fulfilled`, `voided`, `on_hold`), so a client generated from it could reject a real order. On `POST /v1/orders`, `order_status` is limited to `draft` only for a `sales_order` or `invoice`. The refusals of the order, refund, settings and deposit endpoints are now listed with their `code` values on each response. **October 2026: a pair of bank lines in transit at a month end is an open item there.** `GET /v1/entities/{entity_id}/reconciliation/account-audit`, `answers.books_against_bank`, each `month_ends` row: when the two bank lines of a pair matched together to one bill payment (a wire and its return) fall on either side of that date, `bank_unbooked_amount` and `bank_unbooked_count` now include the line already in the bank, and `gl_uncleared_amount` and `gl_uncleared_count` include the payment's bank leg; `explained_by_open_items` therefore explains that date instead of leaving the part in transit unexplained. No field is renamed and no other date moves; once both lines are in the bank the pair counts nowhere, as every other match. **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: /vendor-prepayments/{id}/unapply: parameters: - name: id in: path required: true schema: type: string format: uuid description: Vendor prepayment UUID. - name: Idempotency-Key in: header required: false schema: type: string description: >- Optional idempotency key; a retry returns the first result, even after the application row is gone. post: tags: - Purchasing summary: Reverse a vendor prepayment application description: >- Takes one application of a vendor prepayment back off its bill: the application's journal entry is reversed (dated `effective_date` in an open period, else the entity's calendar day), the application is removed, and the bill's paid amount and balance due and the prepayment's balance are restored. The payment holds follow the state the reversal leaves (`holds_plan`): the bill and every other bill of the vendor on the prepayment's purchase order that has money to pay and to which open prepayment money is proposed again, and that no waiver names, is held again (`payment_hold` for this bill, `restored_bill_holds` for the others), whatever write had released it (the hold a system release took off comes back when its text still names exactly the open money, else a fresh hold names it); a person's `unrelieved_prepayment` hold that a full relief ended comes back on this bill, a hold a person released stays released for the prepayments it waived, and a paid or voided bill is never held again. Requires `ap:write` scope, and the call is refused 404 `prepayment_application_not_found`, or 409 `bill_header_unapply_unsupported` (nothing written) where the AP balance writer cannot yet give the amount back. operationId: unapplyVendorPrepaymentV1 requestBody: required: true content: application/json: schema: type: object required: - application_id properties: application_id: type: string format: uuid description: >- The application to take back (from the bill or the prepayment's applications). reason: type: string nullable: true effective_date: type: string format: date nullable: true responses: '200': description: >- The application was un-applied (or, on a retried key, the first result). content: application/json: schema: type: object properties: data: type: object properties: prepayment_id: type: string format: uuid prepayment_number: type: string application_id: type: string format: uuid bill_id: type: string format: uuid bill_number: type: string amount_unapplied: type: number prepayment_balance: type: number prepayment_status: type: string enum: - active - partially_applied bill_balance_due: type: number bill_status: type: string journal_entry_id: type: string format: uuid nullable: true reversal_journal_entry_id: type: string format: uuid nullable: true entry_disposition: type: string enum: - reversed - already_reversed - no_entry entry_date: type: string format: date payment_hold: type: object nullable: true description: >- The application's own bill put on hold again (the automatic hold, because open prepayment money is proposed to it again, or a person's hold a full relief had ended); null when its hold does not change. A view of holds_plan. properties: bill_id: type: string format: uuid bill_number: type: string outcome: type: string enum: - restored - placed - already_held payment_hold_type: type: string nullable: true cause: type: string hold: type: string enum: - automatic - person restored_bill_holds: type: array description: >- The other bills on the prepayment's purchase order put on hold again because open prepayment money is proposed to them again (whichever write had released them). The application's own bill is `payment_hold`. A view of holds_plan. items: type: object properties: bill_id: type: string format: uuid bill_number: type: string outcome: type: string enum: - restored - placed - already_held payment_hold_type: type: string nullable: true cause: type: string hold: type: string enum: - automatic - person holds_plan: type: array items: $ref: '#/components/schemas/VendorPrepaymentHoldChange' description: Every hold this un-apply changed. idempotent_replay: type: boolean '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' '422': $ref: '#/components/responses/Error' '500': $ref: '#/components/responses/Error' security: - ApiKeyAuth: [] components: schemas: VendorPrepaymentHoldChange: type: object description: >- One payment hold a vendor prepayment write changed (or, in a preview, will change). The automatic unrelieved_prepayment hold follows one rule over state: a bill of the vendor with money left to pay is held while an open prepayment of the vendor is proposed to it (on one of its purchase orders; a landed-cost prepayment only on a bill with a landed line) that no waiver on the bill names, and is not held otherwise. A person's release of such a hold is a waiver for the prepayments open at that moment; a later deposit, or one that re-opens, holds the bill again. A hold a person placed is never changed by the rule, except that a person's unrelieved_prepayment hold ended by a full relief comes back when an un-apply reopens the bill. A write decides the hold of its own bill (a new bill; the bill an application names) in its own transaction, and the holds of the other bills on the purchase order right after it commits, before it answers. When another change holds one of those bills at that moment, the write is not refused and not rolled back: the entry reads `outcome: deferred`, and the next prepayment movement on the same purchase order reconciles that bill. properties: bill_id: type: string format: uuid bill_number: type: string hold: type: string enum: - automatic - person description: >- automatic: the rule's hold; person: a hold a person placed (its full-relief release, or that release undone). from: type: string enum: - held - not_held to: type: string enum: - held - not_held description: >- held: the write puts the bill on hold (a preview's entry with to = held is a hold the write will place or put back). cause: type: string enum: - open_prepayment - no_open_prepayment - waived - full_relief - bill_closed - full_relief_undone description: >- open_prepayment: open prepayment money is proposed to the bill; no_open_prepayment: none is; waived: every open prepayment proposed to it is in its waiver; full_relief: the bill is relieved in full; bill_closed: the bill is written off; full_relief_undone: a person's hold a full relief ended is back because the bill is no longer relieved in full. prepayment_numbers: type: array items: type: string description: >- To held: the open prepayments the hold names. To not_held: the open prepayments still proposed (waived), else empty. prepayment_ids: type: array items: type: string format: uuid outcome: type: string enum: - placed - restored - already_held - released - already_released - deferred description: >- On a write only. restored: the hold a system release took off is back exactly (its time and holder kept); placed: a fresh hold naming the money open now; already_held / already_released: the bill changed under the write and nothing was written; deferred: another change held the bill when the write reconciled it, so its hold is unchanged for now (the entry says what it should become) and the next prepayment movement on the same purchase order reconciles it. 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. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.