Prevent preorder overselling with Shopify Flow

STOQ starts a preorder on a product only once it is completely out of stock (inventory reaches zero), not partway through its remaining stock. If a product still has stock left, is enrolled in a preorder offer, and has Continue selling when out of stock enabled, a customer can order more than the real available quantity. For example, if 3 units are in stock and a customer orders 4, the extra unit does not automatically become a preorder, and the product oversells.

Use this guide if you run specific-products preorder offers and want the out-of-stock to preorder handoff to happen automatically without overselling. The two Shopify Flow workflows below keep Continue selling off while real stock is available, then enable it the moment inventory hits zero, so STOQ preorders take over cleanly. A second workflow turns it back off when you restock.

Before you begin

How it works

The two workflows toggle one Shopify setting, Continue selling when out of stock, based on live inventory:

• Inventory reaches zero, Continue selling turns on, and STOQ starts accepting preorders.
• You restock, Continue selling turns off, and the product resumes normal in-stock selling until it sells out again.

Together they make the out-of-stock to preorder transition automatic, with no manual toggling.

Set it up

Import both workflows so the transition works in both directions. Flow 1 enables preorders at stockout; Flow 2 restores normal selling on restock.

Flow 1: enable Continue selling on stockout

This workflow enables Continue selling the moment a variant hits zero, so STOQ can immediately accept preorders on it.

• Trigger: Inventory quantity changed. This tracks the inventory level directly, so it is not tied to order creation.
• Condition: the variant has a selling plan attached (it is part of an active preorder offer) and its available inventory equals 0.
• Action: enable Continue selling when out of stock on that variant.

What happens once it is on:

1. A customer buys the product and inventory decreases.
2. Inventory reaches 0.
3. The workflow enables Continue selling on that variant.
4. Preorder purchasing becomes available immediately for the sold-out variant.

Download the workflow file: Update product when variant inventory reaches zero with selling plans.flow

Flow 2: disable Continue selling on restock

This reverse workflow turns Continue selling back off after a restock, so the product returns to normal selling instead of accepting preorders indefinitely.

• Trigger: Inventory quantity changed (a restock).
• Action: disable Continue selling when out of stock on the affected variant.

What happens once it is on:

1. You restock the product or update its inventory.
2. The workflow disables Continue selling.
3. The product resumes normal in-stock selling until it sells out again, at which point Flow 1 re-triggers.

Download the workflow file: Disable continue selling.flow

Import a workflow file

Repeat these steps for each of the two files.

Check your setup

1. On a test product with a small stock count that is enrolled in a preorder offer, place orders until inventory reaches 0.
2. Open the product in Shopify admin and confirm Continue selling when out of stock is now enabled, and that the preorder button appears on the live storefront.
3. Restock the product and confirm Continue selling switches back off and the product sells normally again.
4. In Shopify Flow, open each workflow and click Run history to see recent runs and any errors.

Troubleshooting

FAQ

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