Shopify Flow can notify a buyer when a variant's inventory crosses a chosen threshold. That is a useful starting point for a small catalog. The buyer still needs to check stock at the relevant location, incoming orders, supplier lead time and the amount to purchase.
This guide covers the threshold workflow and how to evaluate a more connected replenishment process. Check current Shopify features and your plan rather than assuming every store has the same interface or automation options.
Quick answer: low-stock alerts with Shopify Flow
- Check that Shopify Flow is available for your plan, then install it from Shopify's App Store if needed
- Start from Flow's template library — there's a ready-made template called "Get notified by email when product variant inventory is low" — or create a workflow from scratch
- Use the trigger "Product variant inventory quantity changed"
- Add a condition so it fires once at the crossing, not on every subsequent sale: inventory quantity is less than your threshold and prior quantity was at or above it (e.g., quantity < 5 and prior quantity >= 5)
- Add the action: send an internal email, or use Flow's related templates that email a vendor to reorder or hide the product when it hits zero
Test the workflow with a controlled inventory change and inspect its run history. Check location-level availability explicitly: a total across locations can hide a shortage at the store that needs stock. Shopify documents the prior-quantity field, location variables and notification templates in its inventory trigger reference.
What about reorder points?
A reorder point is a buying threshold, commonly based on expected demand during supplier lead time plus safety stock. You can use a calculated reorder point as a Flow threshold. The important questions are how that value was derived, when it is reviewed and which stock quantity the workflow compares with it.
Shopify also provides native purchase orders and inventory transfers. A draft PO can be marked Ordered after supplier confirmation, then linked to a transfer for shipments and receiving. Verify how any Sidekick-assisted planning or custom Flow workflow behaves in your store. Shopify purchase-order documentation.
If you previously used Stocky, use the Stocky migration guide to review the current replacement workflow and retained historical records.
Where the threshold approach breaks down
A threshold is useful only when its inputs and follow-up match the buying process. Check these conditions before adding another application:
- Demand and lead time: review the threshold when sales patterns or supplier timing change. A fixed value can remain appropriate for stable conditions; it should not be assumed current indefinitely.
- Location scope: identify whether the comparison uses a variant total or one location’s available quantity. Do not compare a location quantity with a prior total across all locations and assume it represents a location-level crossing.
- Incoming coverage: check accepted orders and their arrival dates before buying again. A simple quantity condition does not establish whether an incoming delivery covers the gap in time.
- An owner after the alert: assign someone to review the quantity, supplier pack, minimums and delivery requirements, then create and send the order through the chosen route.
For an illustrative item selling four units per day with a five-day lead time and a chosen eight-unit buffer, the reorder point is 4 × 5 + 8 = 28 units. That number could be configured in an alert. It is not necessarily the quantity to buy.
If the buyer instead chooses an order-up-to target of 60 units, with 20 usable uncommitted units and 12 confirmed incoming in time, the proposed purchase is 60 − 20 − 12 = 28 units. In twelve-unit cases, rounding up means 36 units, giving a position of 68. Check capacity and cash before accepting that rounding. The identical 28 in these two examples is coincidental: trigger threshold and purchase quantity answer different questions.
Test the crossing and the response
With the example condition “current quantity below 5 and prior quantity at least 5,” a change from 6 to 4 should alert, while 4 to 3 should not. Replenishing to 8 and then dropping to 4 creates another crossing. A product already below the threshold when you activate the workflow may not produce that crossing event; review existing shortages during setup.
Use controlled changes to inspect the run history, notification recipient and location scope. Include a manual adjustment or integration-driven update, because Shopify documents that inventory changes from those sources can also trigger the workflow. Check the actual template or custom logic rather than assuming every low-stock email behaves the same way.
Evaluate the complete replenishment workflow
If maintaining thresholds or acting on alerts is becoming costly, test a connected workflow with the same item and supplier. Inspect how it proposes quantities, represents packs and minimums, accounts for existing orders, and handles a changed supplier confirmation. Ask which inputs are automatic and which remain configured or manually reviewed.
LineNow’s Shopify purchasing workflow connects buying with supplier POs, replies and receiving around a living purchase order. Confirm supported supplier channels and item/location mappings. Check arrival timing separately rather than assuming any aggregate incoming quantity covers an earlier need.
Define who owns inventory updates and accounting records so a receipt is posted once. The Shopify procurement guide covers that broader evaluation.
Reviewed Flow alerts and native purchasing may be sufficient. There is no universal SKU count that requires another system; compare the actual maintenance work, missed follow-up and correction effort with the proposed workflow.
Sources checked
- Shopify Help: Shopify Flow — Product variant inventory quantity changed trigger
- Shopify Help: Shopify Flow workflow examples
- Shopify Help: Migrating from Stocky to Shopify inventory management
- Shopify blog: Enhanced inventory management (June 2026)