How does the 'Add/Deduct with existing quantity' function work in Stock Sync?

The 'Add/Deduct with existing quantity' function lets Stock Sync increase or decrease inventory based on the value in your supplier’s file rather than replacing the existing quantity. When a feed is set to Add/Deduct, the app takes the current Shopify stock for that product and adds the amount from the feed file on top of it.

For example, if a product has 50 units in Shopify and the feed file shows a quantity of 30, an Add/Deduct feed will update the stock to 80. This is often used in multi‑feed setups where one feed overwrites the base stock and the remaining feeds add additional supplier or warehouse quantities. If the wrong quantities accumulate, you may need to change the feed’s Quantity option from Add/Deduct to Overwrite.

Updated on: 10/07/2026