Keep stock in sync

This guide keeps a store's stock in step with another system, such as a warehouse, an ERP or a second shop's point of sale.

Nepzio counts stock as the store sells, online and in the shop. Decide which system holds the true count:

The other system holds it: push counts into Nepzio with POST /v1/inventory/set.
Nepzio holds it: read Nepzio's counts with GET /v1/inventory and the inventory.updated webhook.

Pushing counts into Nepzio

Needs a key with write_inventory. Name each variant by its SKU (or variant_id).

To make the count exactly what the other system says (after a stock count, say):

curl https://api.nepzio.com/v1/inventory/set \
  -H "Authorization: Bearer $NEPZIO_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 3c9f..." \
  -d '{"sku": "PSH-RED", "stock": 42, "reason": "Warehouse count"}'

To add or take away (stock received, items damaged):

curl https://api.nepzio.com/v1/inventory/adjust \
  -H "Authorization: Bearer $NEPZIO_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 8a21..." \
  -d '{"sku": "PSH-RED", "delta": 10, "reason": "Received from supplier"}'

No lost sales: both work out the change at the moment it is saved, under a lock, so a sale made at the same moment isn't lost.
Never below zero: a change that would take stock below zero is refused with insufficient_stock.
On the record: each change appears in the store's stock history with your reason, credited to your key.
Safe to retry: send an Idempotency-Key with each change.

Reading Nepzio's counts

Needs read_inventory. Each variant has one stock level:

{
  "object": "inventory_level",
  "variant_id": "...",
  "product_id": "...",
  "sku": "PSH-RED",
  "tracked": true,
  "stock": 42,
  "reserved": 3,
  "available": 39,
  "updated_at": "2026-11-10T08:15:00Z"
}

stock: units on hand.
reserved: units held by orders not yet shipped.
available: what can be sold now (stock less reserved). It is null for a variant whose quantity isn't tracked, meaning there is no limit.

Fetch only some variants with ?sku=PSH-RED,PSH-BLUE (up to 100), or what changed with ?updated_at_min=.... Listen for inventory.updated to hear about changes as they happen. Several changes within a few seconds arrive as one event.