Purchase-to-Pay Flow - Arcus ERP Docs

What this guide covers

The purchase-to-pay (P2P) workflow moves goods and money through four stages:

Purchase order — commit to buying from a vendor
Goods receipt — receive the goods into inventory
Vendor bill — record the vendor’s invoice and clear the GRNI accrual
AP payment — pay the bill and close the liability

Each stage is a separate API call. GL entries post automatically at the right stage. No manual journal entries are needed for the standard flow.

Prerequisites

API key with scopes: purchasing:write, purchasing:read, accounting:write
An active vendor account (account_type: vendor)
One or more product IDs to order
A warehouse location ID

Stage 1: Create the purchase order

POST /v1/orders with document_type: "purchase_order". The order is created in draft status. No GL entry fires at this stage.

curl -s -X POST "https://api.arcuserp.com/v1/orders" \
  -H "Authorization: Bearer $ARCUS_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: po-acme-2026-05-12-001" \
  -d '{
    "document_type": "purchase_order",
    "account_id": "acct_acme_vendor_uuid",
    "location_id": "loc_main_warehouse_uuid",
    "payment_terms": "Net30",
    "line_items": [
      {
        "product_id": "prod_dome_riser_uuid",
        "quantity": 24,
        "cost_rate": 18.00,
        "notes": "Dome Riser Kit - Q2 restock"
      },
      {
        "product_id": "prod_flat_riser_uuid",
        "quantity": 12,
        "cost_rate": 15.00
      }
    ]
  }'

import Arcus from "@arcuserp/sdk";

const arcus = new Arcus({ apiKey: process.env.ARCUS_API_KEY });

const po = await arcus.orders.create({
  document_type: "purchase_order",
  account_id: "acct_acme_vendor_uuid",
  location_id: "loc_main_warehouse_uuid",
  payment_terms: "Net30",
  line_items: [
    {
      product_id: "prod_dome_riser_uuid",
      quantity: 24,
      cost_rate: 18.00,
      notes: "Dome Riser Kit - Q2 restock",
    },
    {
      product_id: "prod_flat_riser_uuid",
      quantity: 12,
      cost_rate: 15.00,
    },
  ],
}, { headers: { "Idempotency-Key": "po-acme-2026-05-12-001" } });

console.log(po.data.order_number); // PO-00042
console.log(po.data.status);       // draft

import arcuserp, os

client = arcuserp.Arcus(api_key=os.environ["ARCUS_API_KEY"])

po = client.orders.create(
    document_type="purchase_order",
    account_id="acct_acme_vendor_uuid",
    location_id="loc_main_warehouse_uuid",
    payment_terms="Net30",
    line_items=[
        {
            "product_id": "prod_dome_riser_uuid",
            "quantity": 24,
            "cost_rate": 18.00,
            "notes": "Dome Riser Kit - Q2 restock",
        },
        {
            "product_id": "prod_flat_riser_uuid",
            "quantity": 12,
            "cost_rate": 15.00,
        },
    ],
    extra_headers={"Idempotency-Key": "po-acme-2026-05-12-001"},
)

print(po.data.order_number)  # PO-00042
print(po.data.status)        # draft

Save po.data.id (the PO UUID). You will reference it in later stages.

Confirm the PO (open it)

Once reviewed, transition to open status, which makes it eligible for receiving:

curl -s -X PATCH "https://api.arcuserp.com/v1/orders/$PO_ID" \
  -H "Authorization: Bearer $ARCUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"status": "open"}'

Stage 2: Receive goods

POST /v1/orders/{po_id}/receive records the goods arriving at your warehouse. GL entries that fire at this stage:

Account	Debit	Credit
Inventory (Finished Goods)	unit_cost x qty_received
GRNI (Goods Received Not Invoiced)		unit_cost x qty_received

GRNI is a liability accrual that stays open until you post the vendor bill in Stage 3.

curl -s -X POST "https://api.arcuserp.com/v1/orders/$PO_ID/receive" \
  -H "Authorization: Bearer $ARCUS_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: recv-po-00042-2026-05-14" \
  -d '{
    "received_date": "2026-05-14",
    "location_id": "loc_main_warehouse_uuid",
    "line_items": [
      {
        "order_item_id": "oi_dome_riser_uuid",
        "quantity_received": 24,
        "bin_id": "bin_A1_uuid"
      },
      {
        "order_item_id": "oi_flat_riser_uuid",
        "quantity_received": 12,
        "bin_id": "bin_A2_uuid"
      }
    ]
  }'

const receipt = await arcus.orders.receive(poId, {
  received_date: "2026-05-14",
  location_id: "loc_main_warehouse_uuid",
  line_items: [
    { order_item_id: "oi_dome_riser_uuid", quantity_received: 24, bin_id: "bin_A1_uuid" },
    { order_item_id: "oi_flat_riser_uuid", quantity_received: 12, bin_id: "bin_A2_uuid" },
  ],
}, { headers: { "Idempotency-Key": "recv-po-00042-2026-05-14" } });

console.log(receipt.data.id);                    // receipt UUID
console.log(receipt.data.inventory_updated);     // true

receipt = client.orders.receive(
    po_id,
    received_date="2026-05-14",
    location_id="loc_main_warehouse_uuid",
    line_items=[
        {"order_item_id": "oi_dome_riser_uuid", "quantity_received": 24, "bin_id": "bin_A1_uuid"},
        {"order_item_id": "oi_flat_riser_uuid", "quantity_received": 12, "bin_id": "bin_A2_uuid"},
    ],
    extra_headers={"Idempotency-Key": "recv-po-00042-2026-05-14"},
)

print(receipt.data.id)

The response includes inventory_updated: true and the GL journal entry ID for the GRNI posting. Inventory on-hand increases immediately. Partial receipt: you can receive fewer than the ordered quantity. The remaining quantity stays open on the PO. Fire another receive call when the rest arrives.

Stage 3: Enter and post the vendor bill

When the vendor’s invoice arrives, create a vendor bill linked to the PO. Posting the bill clears the GRNI accrual and records the AP liability.

Create the draft bill

curl -s -X POST "https://api.arcuserp.com/v1/vendor-bills" \
  -H "Authorization: Bearer $ARCUS_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: bill-acme-inv-20260514" \
  -d '{
    "vendor_id": "acct_acme_vendor_uuid",
    "po_id": "'"$PO_ID"'",
    "vendor_invoice_number": "INV-2026-0514",
    "bill_date": "2026-05-14",
    "due_date": "2026-06-13",
    "line_items": [
      {
        "po_item_id": "oi_dome_riser_uuid",
        "quantity": 24,
        "unit_cost": 18.00,
        "description": "Dome Riser Kit"
      },
      {
        "po_item_id": "oi_flat_riser_uuid",
        "quantity": 12,
        "unit_cost": 15.00,
        "description": "Flat Riser Kit"
      }
    ]
  }'

The bill is created in draft status. No GL entry yet.

Post the bill

curl -s -X POST "https://api.arcuserp.com/v1/vendor-bills/$BILL_ID/post" \
  -H "Authorization: Bearer $ARCUS_API_KEY"

GL entries that fire when the bill is posted:

Account	Debit	Credit
GRNI (Goods Received Not Invoiced)	total bill amount
Accounts Payable		total bill amount

This clears the GRNI accrual from Stage 2. The AP liability is now open until Stage 4.

Stage 4: Pay the vendor bill

POST /v1/ap-payments closes the AP liability and records the outgoing cash.

curl -s -X POST "https://api.arcuserp.com/v1/ap-payments" \
  -H "Authorization: Bearer $ARCUS_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: ap-pay-bill-20260613" \
  -d '{
    "vendor_id": "acct_acme_vendor_uuid",
    "payment_date": "2026-06-13",
    "payment_method": "check",
    "bank_account_id": "bank_operating_uuid",
    "memo": "Acme Inv 2026-0514 - Dome/Flat Riser restock",
    "applications": [
      {
        "bill_id": "'"$BILL_ID"'",
        "amount": 612.00
      }
    ]
  }'

const payment = await arcus.apPayments.create({
  vendor_id: "acct_acme_vendor_uuid",
  payment_date: "2026-06-13",
  payment_method: "check",
  bank_account_id: "bank_operating_uuid",
  memo: "Acme Inv 2026-0514 - Dome/Flat Riser restock",
  applications: [
    { bill_id: billId, amount: 612.00 },
  ],
}, { headers: { "Idempotency-Key": "ap-pay-bill-20260613" } });

console.log(payment.data.check_number); // CHK-00142 (if payment_method = "check")
console.log(payment.data.status);       // posted

payment = client.ap_payments.create(
    vendor_id="acct_acme_vendor_uuid",
    payment_date="2026-06-13",
    payment_method="check",
    bank_account_id="bank_operating_uuid",
    memo="Acme Inv 2026-0514 - Dome/Flat Riser restock",
    applications=[
        {"bill_id": bill_id, "amount": 612.00},
    ],
    extra_headers={"Idempotency-Key": "ap-pay-bill-20260613"},
)

print(payment.data.check_number)  # CHK-00142

GL entries that fire at payment:

Account	Debit	Credit
Accounts Payable	612.00
Bank (Operating Checking)		612.00

The AP liability is cleared. The vendor bill transitions to paid status.

GL summary: the full P2P transaction trail

Stage	Event	Debit	Credit
2	Receive goods	Inventory FG	GRNI
3	Post vendor bill	GRNI	Accounts Payable
4	Pay bill	Accounts Payable	Bank

At Stage 4, GRNI nets to zero and Inventory FG reflects the real cost. This is the standard accrual accounting pattern (NetSuite, Acumatica, QuickBooks Enterprise all follow the same sequence).

Partial payments and multi-bill payments

A single AP payment can apply to multiple bills:

{
  "applications": [
    { "bill_id": "bill_uuid_1", "amount": 432.00 },
    { "bill_id": "bill_uuid_2", "amount": 180.00 }
  ]
}

You can also pay a bill partially. The bill remains open with a reduced balance_due until the remaining balance is paid or written off.

Vendor credits

To apply a vendor credit against a bill payment, include vendor_credit_ids[] in the payment body:

{
  "vendor_credit_ids": ["vc_uuid_1"],
  "applications": [
    { "bill_id": "bill_uuid", "amount": 462.00 }
  ]
}

The credit reduces the cash portion of the payment. If credits fully cover the bill, no bank JE posts.

Common errors

Code	HTTP	Meaning
`po_not_found`	404	PO UUID does not exist for this entity
`po_not_receivable`	422	PO status is not `open` or `processing`
`quantity_exceeds_ordered`	422	Receipt line quantity exceeds PO line quantity remaining
`bill_already_posted`	409	Attempted to post a bill that is already in `open` status
`bill_balance_insufficient`	422	Payment application amount exceeds bill balance due
`bank_account_not_found`	404	`bank_account_id` does not exist for this entity
`insufficient_scope`	403	API key missing `purchasing:write` or `accounting:write` scope

Idempotency

Every write in this flow accepts Idempotency-Key. Use a stable key tied to your source record (e.g. po-<source-po-id>, recv-<source-receipt-id>, bill-<vendor-invoice-number>). Keys expire after 24 hours.

Verifying the full chain

After all four stages, run these checks:

# Confirm PO is fulfilled
curl "https://api.arcuserp.com/v1/orders/$PO_ID" \
  -H "Authorization: Bearer $ARCUS_API_KEY"
# Expect: status = fulfilled or processing

# Confirm inventory increased
curl "https://api.arcuserp.com/v1/inventory?product_id=prod_dome_riser_uuid" \
  -H "Authorization: Bearer $ARCUS_API_KEY"
# Expect: on_hand increased by 24

# Confirm bill is paid
curl "https://api.arcuserp.com/v1/vendor-bills/$BILL_ID" \
  -H "Authorization: Bearer $ARCUS_API_KEY"
# Expect: status = paid, balance_due = 0

# Run AP aging to confirm no residual payable
curl "https://api.arcuserp.com/v1/reports/ap-aging" \
  -H "Authorization: Bearer $ARCUS_API_KEY"

Next steps

Journal Entries and Period Close — record adjusting entries and close the accounting period
Creating Orders — build a sales order on the outbound side
API Reference: Purchase Orders
API Reference: Vendor Bills
API Reference: AP Payments

​What this guide covers

​Prerequisites

​Stage 1: Create the purchase order

​Confirm the PO (open it)

​Stage 2: Receive goods

​Stage 3: Enter and post the vendor bill

​Create the draft bill

​Post the bill

​Stage 4: Pay the vendor bill

​GL summary: the full P2P transaction trail

​Partial payments and multi-bill payments

​Vendor credits

​Common errors

​Idempotency

​Verifying the full chain

​Next steps