Substitutions Help App Store listing

How substitutions work

The variant keeps selling

Normally, Shopify stops selling a variant when it runs out. While a rule is on and at least one backup is in stock, the app turns on Continue selling when out of stock for that variant, so customers can still buy it.

  • If every backup runs out too, the app turns Continue selling off, so you don't take orders you can't fill.
  • When you turn a rule off, the app turns Continue selling off for that variant.

The order is swapped right after it's placed

When an order comes in for the sold-out variant, the app edits the order before you fulfill it:

  1. It checks your backups in order, top to bottom, and picks the first one that's in stock.
  2. It replaces the sold-out item with that backup. If you set units per order (for example, 2 small packs for 1 large), it adds that many. See Quantity substitutions.
  3. It holds the order's fulfillment for the moment it takes to edit, then releases it.
  4. It tags the order.

Other items on the order aren't touched.

Order tags

  • Substitutions: success means a backup was swapped in.
  • Substitutions: skipped means the order had an item a rule covers, but it couldn't be swapped (for example, every backup was out of stock). Check these orders by hand.

You can filter orders by these tags in the Shopify admin.

What the customer pays

The customer pays what they paid at checkout.

  • If the backup costs more, the app adds a discount to the new line so it bills at the original amount. You absorb the difference.
  • If the backup costs less, Shopify shows the difference on the order. You decide whether to refund it.

What the customer sees

Checkout doesn't change. The app doesn't send the customer an email about the swap; the order in your admin shows the edit.

When a rule doesn't swap

  • Inventory tracking is off for the variant, so Shopify never reports it sold out. The rule shows Needs attention.
  • Every backup is out of stock. The rule shows Needs attention and the order is tagged Substitutions: skipped.
  • You've reached your plan's order limit for this billing cycle. See Plans and limits.