Add a single line item to an order

Adds a single line item to an order in draft or confirmed status. Validates that the product is active and belongs to the entity. Runs the pricing engine (qty-break tiers, account pricing level) to compute sell_rate if not overridden. Triggers fullRecalculateOrder after insert. Idempotent via Idempotency-Key. Requires orders:write scope.

A line cannot be added to a CLOSED AR document: a cancelled/voided order, a posted/fulfilled order (returns edit_not_allowed with suggested_action: create_return), or a billed-and-paid / fully-paid order (invoice_status in paid/overdue or payment_status = paid; returns edit_not_allowed with suggested_action: revise_order). To revise a paid order, pass override: true in the body with the orders.revision_override permission; the edit then proceeds, the order’s revision_count increments, and the override is recorded in the activity log. The customer must re-acknowledge the new total.

POST /orders/{id}/items

Add a single line item to an order

cURL

curl --request POST \
  --url https://api.arcuserp.com/v1/orders/{id}/items \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "product_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "quantity": 2,
  "variant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "sell_rate": 123,
  "unit_price": 123,
  "list_price": 123,
  "notes": "<string>",
  "override": true,
  "override_reason": "<string>"
}
'

200

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "entity_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "order_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "product_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "variant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "sku": "<string>",
  "title": "<string>",
  "quantity": 123,
  "quantity_fulfilled": 123,
  "quantity_returned": 123,
  "received_floor": 123,
  "line_editability": {
    "qty": {
      "allowed": true,
      "reason": "po_pending_approval_edit_locked",
      "floor": 123
    },
    "unit_cost": {
      "allowed": true,
      "reason": "po_pending_approval_edit_locked",
      "warn_received_qty": 123
    },
    "delete": {
      "allowed": true,
      "reason": "po_pending_approval_edit_locked"
    },
    "notes": {
      "allowed": true,
      "reason": "po_pending_approval_edit_locked"
    }
  },
  "sell_rate": 123,
  "unit_price": 123,
  "list_price": 123,
  "pricing_rule_adjustment": 123,
  "coupon_adjustment": 123,
  "discount_amount": 123,
  "line_subtotal": 123,
  "tax_amount": 123,
  "line_total": 123,
  "adjustments": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "source_type": "<string>",
      "source_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "source_label": "<string>",
      "per_unit_amount": 123,
      "quantity": 123,
      "line_amount": 123,
      "proration_ratio": 123,
      "applied_at": "2023-11-07T05:31:56Z"
    }
  ],
  "unit_cost": 123,
  "weight": 123,
  "is_tax_exempt": true,
  "product_tax_code": "<string>",
  "sort_order": 123,
  "product_vendor_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z"
}

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.

Headers

Idempotency-Key · string

Client-generated unique key for idempotent POST/PATCH/DELETE operations. Alias for the Idempotency parameter. Max 255 chars. On retry with the same key, the original response is returned without re-executing the operation. Keys expire after 24 hours.

Maximum string length: 255

Path Parameters

id · string<uuid> · required

Body

application/json

product_id · string<uuid> · required

quantity · integer · required

Required range: x >= 1

variant_id · string<uuid>

sell_rate · number

Override unit price (canonical Arcus field).

unit_price · number

Alias of sell_rate (Stripe/Shopify convention). Either name accepted. Both with different values returns 400; negative/zero returns 422. When applied price differs from catalog list_price, response carries warnings array entries plus emits order.price_override audit row.

list_price · number

notes · string

override · boolean

Set true (with the orders.revision_override permission) to revise a paid/billed order by adding this line. Without it, a paid/billed order returns 422 edit_not_allowed (suggested_action revise_order).

override_reason · string

Optional reason recorded in the audit log when override is used.

Response

200

application/json

Added order item. Response includes unit_price alias of sell_rate. When override detected, response also carries warnings array entries (item, code price_override, product_id, catalog_price, applied_price, delta).

A line item on an order. Sub-resource of Order.

id · string<uuid>

entity_id · string<uuid> · read-only

Multi-tenant scoping column (Layer 1 isolation). Set automatically from the parent orders.entity_id and enforced by Postgres trigger trg_order_items_entity_parity (P0-ENTITY-ID-CHILD-TABLES, 2026-05-18). Cross-tenant writes are rejected at the database layer.

order_id · string<uuid>

product_id · string<uuid> | null

variant_id · string<uuid> | null

sku · string | null

title · string

quantity · integer

quantity_fulfilled · integer · read-only

quantity_returned · integer · read-only

received_floor · number · read-only

PURCHASE-ORDER lines only. The lowest quantity this line may be reduced to: the SAFEST of the line's quantity_fulfilled and its receipted-plus-damaged total, clamped at 0. The two sources disagree on migrated rows and on rows whose receipt was undone, so the maximum of both is used -- it can only ever refuse a reduction that either source forbids.

line_editability · object

PURCHASE-ORDER lines only. Per-field verdicts from the same predicate the write handlers enforce, so a client never has to restate the stage rules.

Show child attributes

sell_rate · number

Canonical Arcus per-unit price column (matches order_items.sell_rate).

unit_price · number

Public-API alias of sell_rate (Stripe/Shopify/QuickBooks convention). Always populated on read; equal to sell_rate. Set per NEW-GAP-API-V1-CALLER-UNIT-PRICE-SILENTLY-OVERRIDDEN 2026-05-17 closure.

list_price · number

pricing_rule_adjustment · number · read-only

Per-unit pricing-rule savings (list_price minus sell_rate, positive magnitude). Already baked into sell_rate (and therefore line_subtotal) per ASC 606 transaction-price pricing; surfaced for the gross-to-net bridge display, never re-subtracted.

coupon_adjustment · number · read-only

Per-line allocated coupon/order-level discount (signed; negative for a discount). Reflected in line_subtotal.

discount_amount · number

line_subtotal · number · read-only

tax_amount · number · read-only

line_total · number · read-only

adjustments · object[] · read-only

Per-line, per-source adjustment breakdown from order_item_adjustments (the canonical SSOT). Each entry attributes a signed line_amount to a source (pricing_rule | order_adjustment | coupon | manual_line_override | return_refund_adjust | restocking_fee). Empty array for lines with no allocations (and on legacy orders predating the writer). Industry parity: Shopify Admin GraphQL LineItem.discountAllocations[].

Show child attributes

unit_cost · number | null

weight · number | null

is_tax_exempt · boolean

product_tax_code · string | null

sort_order · integer

product_vendor_id · string<uuid> | null

For purchase_order document_type lines only: exact product_vendors row this line is bound to (NEW-GAP-ORDER-ITEMS-PRODUCT-VENDOR-ID-PROVENANCE, 2026-05-14). NULL for legacy PO lines and all non-PO doc types; PDF falls back to the deterministic default-vendor-part pick.

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

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