Update a purchase order

Updates header-level fields on a purchase order (delivery date, payment due date, receiving location, tracking reference, notes, internal notes). Line items are updated via the items sub-resource.

Editability by stage (2026-08-17). The four OPERATIONAL fields (expected_date, due_date, location_id, po_tracking_reference) are editable while the purchase order is draft, open or processing. On fulfilled and cancelled only notes and internal_notes remain writable, as an annotation. On archived and expired nothing is writable. While approval_status is pending only internal_notes is writable. Any other status is treated as locked (fail-closed). A request that touches a blocked field is refused WHOLE with 422 and the response names the offending fields in blocked_fields; nothing is partially applied. Reason codes: po_status_locked, po_status_unknown_locked, notes_only_on_terminal, po_pending_approval_edit_locked, po_pending_approval_and_terminal.

NOTE: the previous version of this description claimed header edits were limited to status: draft and that “orders in approved or later status require a change-order flow”. Neither was true — this handler had no status gate at all, and approved / sent are not members of the real order_status vocabulary (draft / open / processing / fulfilled / cancelled / archived / expired).

Requires purchasing:write scope.

Drop-ship destination (2026-07-10). shipping_address_id is writable ONLY on a drop-ship-linked PO (a sales-order line sources from it) that is unsent and unreceived; otherwise 422 po_shipto_not_editable, 409 dropship_po_sent_blocks_shipto_change (change it on the parent sales order with propagate_to_sent_pos: true instead), or 409 dropship_po_received_blocks_shipto_change. The address must belong to the entity.

PATCH /purchase-orders/{id}

Update a purchase order

cURL

curl --request PATCH \
  --url https://api.arcuserp.com/v1/purchase-orders/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "expected_date": "2023-12-25",
  "notes": "<string>",
  "payment_term_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "location_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "vendor_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "status": "<string>"
}
'

200

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "object": "purchase_order",
  "entity_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "po_number": "<string>",
  "vendor_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "location_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "status": "draft",
  "po_date": "2023-11-07T05:31:56Z",
  "expected_date": "2023-11-07T05:31:56Z",
  "subtotal": 123,
  "tax_total": 123,
  "shipping_total": 123,
  "po_total": 123,
  "currency": "USD",
  "notes": "<string>",
  "internal_notes": "<string>",
  "metadata": {},
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "approved_total": 123,
  "approval_stale": true,
  "header_editability": {},
  "billed_total": 123,
  "unbilled_balance": 123
}

Authorizations

Authorization · string · header · required

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.

Path Parameters

id · string · required

Purchase order UUID or PO number (e.g. PO-001234). Polymorphic lookup: if the value is not a UUID it is resolved to a UUID via orders.order_number where document_type=purchase_order within the entity scope. (NEW-GAP-API-V1-POLYMORPHIC-LOOKUP-CROSS-RESOURCE 2026-05-20)

Body

application/json

expected_date · string<date>

notes · string

payment_term_id · string<uuid>

location_id · string<uuid>

vendor_id · string<uuid>

status · string

Response

200

application/json

Updated purchase order

A purchase order issued to a vendor.

id · string<uuid>

object · enum<string>

Available options: purchase_order

entity_id · string<uuid> · read-only

po_number · string · read-only

vendor_id · string<uuid>

location_id · string<uuid> | null

status · enum<string> · read-only

Available options: draft, approved, sent, partially_received, received, closed, cancelled

po_date · string<date-time>

expected_date · string<date-time> | null

subtotal · number

tax_total · number

shipping_total · number

po_total · number

currency · string · default: USD

notes · string | null

internal_notes · string | null

metadata · object | null

created_at · string<date-time> · read-only

updated_at · string<date-time> · read-only

approved_total · number | null · read-only

The order total as it stood when an approver approved this purchase order -- the basis they actually saw. NULL on every approval predating 2026-08-17 (no backfill) and NULL means "basis unknown", which is treated as fail-safe.

approval_stale · boolean · read-only

DERIVED, not stored. True when the order is approved AND its total has since risen above approved_total. The purchase order still receives normally; this is a non-blocking prompt to re-approve.

header_editability · object · read-only

Per-field verdicts for the header fields, from the same predicate the write handlers enforce. Keys: notes, internal_notes, due_date, expected_date, location_id, po_tracking_reference. Each is { allowed: boolean, reason: string|null } where reason is a token from the PoLineEditReason vocabulary.

Show child attributes

billed_total · number · read-only

How much of this purchase order's commitment a vendor bill has already taken over: the sum of total over every linked bill in open, partial, paid or written_off. 0 when no bill has been raised, never null.

unbilled_balance · number · read-only

What the purchase order STILL commits the buyer to: max(order_total - billed_total, 0), cents-quantized. Read this rather than balance_due, which on a purchase order is the ORIGINAL COMMITMENT the header was raised for and is never decremented when a bill is raised (the payable is the bill). Clamped at zero because a vendor may add freight on the bill and over-bill the order.