> ## 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. # Set or clear a vendor prepayment's purchase order > Points an open prepayment at a purchase order of the entity, or clears it with `po_id: null`. The order is checked by the same rule as recording a prepayment: a live purchase order of this entity that is not cancelled, archived, expired, closed short or fully billed. `po_link_kind` is `goods` (an advance on its own vendor's order) or `landed` (a freight, customs or duty advance on another vendor's order); omitted, it is computed from the order's vendor (`landed` when the order's vendor is not the prepayment's vendor). Nothing is posted: no journal entry, no balance or application changes. The automatic `unrelieved_prepayment` holds of the old and the new order's bills follow the pointer (`holds_plan`, `released_bill_holds`, `held_bill_holds`). Sending the state the prepayment already has answers `unchanged: true` and writes nothing. Requires `ap:write` scope. Refused 400 `missing_po_id` (the body names no `po_id`), `invalid_po_id`, `invalid_po_link_kind`, `po_link_kind_requires_po`, `invalid_prepayment_id`, `missing_prepayment_id` or `missing_entity_id`; 404 `prepayment_not_found` or `purchase_order_not_found`; 409 `prepayment_not_open` (refunded, voided or fully applied); 422 `purchase_order_not_prepayable` (with a `reason`) or `purchase_order_not_this_vendors` (a `goods` kind on another vendor's order). ## OpenAPI ````yaml /openapi.yaml patch /vendor-prepayments/{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. **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: an inventory adjustment names its reason, a key never names a document's uploader, and the flag refusals are documented.** `POST /v1/inventory/adjustments` accepts `reason_code` (or `adjustment_reason_id`) on a single-item request, at the root of a multi-item request (the reason of every item that sends none of its own) and on each item. The adjustment posts to the account the entity's adjustment reason names for the movement's direction, exactly as the adjustment screen posts it, and the answer names the reason and the account (`adjustment_reason`, `gl_account_source`, `posted_to`). A code that names none of the entity's active reasons is refused 422 `adjustment_reason_not_found` with `param` and the active codes in `allowed_codes`, and nothing is written; a turned-off reason is refused 422 `adjustment_reason_inactive`; a key cannot choose an account other than the reason's (403 `adjustment_account_choice_requires_user`, or 422 with `param` `gl_account_id` for an account the adjustment picker does not offer) and cannot post above a reason's approval limit (403 `adjustment_over_approval_threshold`). Before, `reason_code` was not read: such an adjustment, and a multi-item item's `adjustment_reason_id`, posted where the free text sent them. Deprecated: choosing the account through the free-text `reason`, which picks it by matching words in the text (text that matches none posts to the entity's inventory adjustments account); free text keeps choosing the account as it does today, and no removal date is set. A single-item adjustment answers 200 and a multi-item adjustment 201, as they always have (the page listed only 201). A retry with the same `Idempotency-Key` now answers the first request's response even when a reason, a product, a permission or the posting window changed in between; before, such a retry could answer a refusal for an adjustment that had already been applied. A refusal the adjustment answers (a turned-off reason, a product that holds no stock, the key creator's permission, the posting window) is likewise the answer of its key: once the cause is fixed, send the request with a new key. `POST /v1/documents` and `POST /v1/documents/confirm` never record a person from the request body: a document an API key creates names no uploader, and its activity rows name no user (before, a `user_id` or `uploaded_by` in the body naming an active member of the entity was recorded as that member). Fifteen operations answer 422 `invalid_boolean_field`, with `param` naming the field and nothing written, when a flag is not a JSON `true` or `false`, and each page now says so, naming the flags and the values it refuses: `POST /v1/locations`, `PATCH /v1/locations/{id}`, `POST` and `PATCH /v1/payment-terms`, `PATCH /v1/gl-accounts/{id}`, `PATCH /v1/accounts/{id}`, `POST /v1/accounts/{id}/addresses`, `PATCH /v1/accounts/{id}/addresses/{addr_id}`, `PATCH /v1/accounts/{id}/contacts/{cnt_id}`, `PATCH /v1/kits/{id}`, `POST` and `PATCH /v1/pricing-policies`, `POST /v1/products` (a `pricing` or `purchase_policies` entry), `PATCH /v1/products/{id}` and `POST /v1/products/{id}/pricing`. The text "true" or "false" and 1 are refused on all fifteen (on `PATCH /v1/gl-accounts/{id}` when the body carries no `opening_balance`), and 0 and null on all but `POST /v1/accounts/{id}/addresses`, which reads 0 and null as `false` and creates the address. `PATCH /v1/gl-accounts/{id}` reads its flag only when the body carries no `opening_balance`: a body that carries one posts the account's opening balance and reads no other field. The request bodies of `PATCH /v1/locations/{id}` and `POST /v1/payment-terms`, and the `pricing` entries of `POST /v1/products` and `POST /v1/products/{id}/pricing`, now list those flags as booleans. `POST /v1/locations` lists the fields it reads (`code` is required, the address is one `address` object, and `type`, `description`, `sort_order` and the four flags are listed); `POST /v1/payment-terms` reads `days` and `discount_percent`, not `days_due` and `discount_pct`, and only `name` is required; a listed field the operation does not read now says so. **October 2026: the return create and update contract says what the API does.** On `POST /v1/returns`, `original_order_id` is derived from the lines when it is omitted, and every line names the sales order line it comes back from (`items[].order_item_id`; a line without one is refused 422 `order_line_required`, and that refusal is already live). Deprecated now, and answered on a 201, 400, 404 or 422 answer with a `Deprecation: true` response header and a `Link` to this changelog (plus a `Sunset` header once the removal date is set): `auto_refund: true` and `refund_payment_id` (no longer honored: a return never refunds on its own; issue the refund with `POST /v1/returns/{id}/refund`; at the removal release `auto_refund: true` is refused 422 `auto_refund_removed`; `auto_refund: false` asks for nothing and is not a deprecated use, and the field has no default), and the standalone return, a line that sends `product_id` and no `order_item_id` (already refused; its description leaves the spec at the removal release). `refund_method` lists the values the API accepts (`auto`, `cash`, `credit_memo`, `store_credit`); `original` and `check`, listed before, are refused 400 `invalid_refund_method`. A return line's `condition` lists the values a line stores (`new`, `used`, `damaged`, `defective`); `like_new`, `good` and `fair` were never sent and leave the `ReturnItem` schema one release later. Each return operation's page now names, under the status it is answered with, the refusals with their own `code` that a request sending the fields the page documents can meet, read from the operation's code at every call depth and checked by running it: the operation's own checks (a location or a vendor the request names that is not this entity's among them), the steps it runs (the order line, the replacement order line, the carrier label, the card refund, the vendor-return line) and the ledger and stock refusals it can meet through the return's state or the entity's settings. Not repeated on every page: the refusals every operation shares (the API key, its scopes, its creator's permissions, its network rules, the rate limit and the `Idempotency-Key` header, whose two answers that header's description names); the answers the database gives a value its column does not take, on any field of the path, the query or the body: 400 `invalid_id_format` (not a valid id), 400 `invalid_enum_value` (not a value of the field's type, text where a number belongs among them), 422 `value_too_long` (a text longer than the field holds), 422 `value_out_of_range` (a number larger than the field holds), 400 `not_null_violation`, 400 `check_violation`, 400 `constraint_violated`, 409 `fk_violation` and 409 `uniq_violation` (a value a rule of the database refuses), and 409 `serialization_failure` or 409 `deadlock` (a parallel update; a retry clears it), which a page also names where its own fields were measured to draw one; and an integrity refusal, which reports that records the operation reads disagree with each other and is answered with its own `code`. The two read operations now document their 400 answer, and the add-lines, exchange, advance replacement and vendor return operations the 201 they answer (their pages said 200). The receive-and-dispose lines, the exchange body and the advance replacement lines now list the fields of the contract those operations read for a caller (receive-and-dispose also reads `items[].serial_number_returned`, which is not yet listed); the disposition line lists `vendor_id`, and its `condition` lists the four values a return line stores (`like_new`, `good` and `fair` are still accepted there on a line that sends no `leaves`, where they never block a restock, and leave the list one release later; a kit line that sends `leaves` refuses them 400 `invalid_enum_value`); a documented field an operation does not read now says so. `estimated_refund_amount`, `money_suppression` and `is_pre_settlement` say what the API already did: the estimate is present while neither the lines nor the header hold a credit (the schema said "while no line holds a credit"). A bulk import with `conflict_mode: replace` on returns now answers 409 `return_replace_not_supported` naming the existing return and writes nothing (`MigrationConflictMode` says so); before, it removed the import record from the existing return and created a second return for the same goods. The webhook endpoint's event list counts 152 events in 15 families. The correction documents, the refile, the returns of an order, the receive order, the unexpected arrival and the staff RA PDF stay staff-only for now: they have no api-v1 endpoint in this release. Returns: override_window now needs override_window_reason when a line is outside its return window; returns can span several orders of one customer where Settings > Returns allows it. On `POST /v1/returns`, `return_location_id` names the warehouse the goods come back to (needed when the lines span orders shipped from more than one warehouse), a return across orders names its `refund_method` (`cash`, `credit_memo` or `store_credit`), and a sent `original_order_id` must be the order of one of the lines; `POST /v1/returns/{id}/items` reads `override_window` and `override_window_reason` for a line of an order new to the return. The pages name the refusals: `original_order_not_among_lines`, `return_location_required`, `return_location_not_a_warehouse`, `refund_method_required_multi_order`, `multi_order_tax_filing_not_ready`, `override_window_reason_required`, `approval_required_for_added_lines`, and 404 `location_not_found` for a `return_location_id` that is not one of the entity's locations. **October 2026: credit memos in search, and the cross-resource search answers by scope.** `GET /v1/search/{object}` accepts `credit_memos`: customer credit memos by memo number or customer name, the exact memo number first, each result naming the memo's status, its customer and its return when it has one; it requires the `ar:read` scope in addition to `search:read` (a key without it is refused with 403 `insufficient_scope`), and its cursor (`starting_after`) continues exactly where the previous page ended. `GET /v1/search` now returns matches: each of its five buckets holds results when the key also holds that resource's read scope (`orders:read` for orders and invoices, `products:read` for products, `accounts:read` for accounts, `inventory:read` for serial numbers) and stays empty otherwise; until now every bucket was empty for every key. `meta.did_you_mean` now carries the search term when the results are close matches rather than exact ones. No field is renamed. **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}: parameters: - name: id in: path required: true schema: type: string format: uuid description: Vendor prepayment UUID. patch: tags: - Purchasing summary: Set or clear a vendor prepayment's purchase order description: >- Points an open prepayment at a purchase order of the entity, or clears it with `po_id: null`. The order is checked by the same rule as recording a prepayment: a live purchase order of this entity that is not cancelled, archived, expired, closed short or fully billed. `po_link_kind` is `goods` (an advance on its own vendor's order) or `landed` (a freight, customs or duty advance on another vendor's order); omitted, it is computed from the order's vendor (`landed` when the order's vendor is not the prepayment's vendor). Nothing is posted: no journal entry, no balance or application changes. The automatic `unrelieved_prepayment` holds of the old and the new order's bills follow the pointer (`holds_plan`, `released_bill_holds`, `held_bill_holds`). Sending the state the prepayment already has answers `unchanged: true` and writes nothing. Requires `ap:write` scope. Refused 400 `missing_po_id` (the body names no `po_id`), `invalid_po_id`, `invalid_po_link_kind`, `po_link_kind_requires_po`, `invalid_prepayment_id`, `missing_prepayment_id` or `missing_entity_id`; 404 `prepayment_not_found` or `purchase_order_not_found`; 409 `prepayment_not_open` (refunded, voided or fully applied); 422 `purchase_order_not_prepayable` (with a `reason`) or `purchase_order_not_this_vendors` (a `goods` kind on another vendor's order). operationId: setVendorPrepaymentPurchaseOrderV1 requestBody: required: true content: application/json: schema: type: object required: - po_id properties: po_id: type: string format: uuid nullable: true description: >- The purchase order to point the prepayment at; null clears it. po_link_kind: type: string enum: - goods - landed nullable: true description: 'Omitted: computed from the order''s vendor.' responses: '200': description: >- The prepayment's purchase order was set or cleared, or already was (`unchanged`). content: application/json: schema: type: object properties: data: type: object properties: prepayment_id: type: string format: uuid prepayment_number: type: string vendor_id: type: string format: uuid po_id: type: string format: uuid nullable: true po_number: type: string nullable: true po_link_kind: type: string enum: - goods - landed previous: type: object properties: po_id: type: string format: uuid nullable: true po_number: type: string nullable: true po_link_kind: type: string enum: - goods - landed holds_plan: type: array items: $ref: '#/components/schemas/VendorPrepaymentHoldChange' description: Every hold the move changed. released_bill_holds: type: array items: type: object description: >- The bills whose automatic hold the move ended. A view of holds_plan. held_bill_holds: type: array items: type: object description: >- The bills the move put on the automatic hold. A view of holds_plan. unchanged: 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.