Working within the Shopify framework, products cannot have multiple price points. To workaround this, Quantity Breaks creates variants for each price tier. After all, it's the same product, just sold at a different price based on how many items the customer has in their cart.
The way the Quantity Breaks app is designed to work is in the cart, the app will swap out the regular priced variant, and replace it with the tiered pricing variant.The variants created by Quantity Breaks on their own do not have inventory tracking. When looking at the variants from within Shopify, the inventory will appear as N/A. This is expected.
Should I add the quantity on each the variants?
No. Changing the inventory value on the Quantity Break variants will skew the actual stock on hand. If you have 10 in stock, those would be represented on the parent (1+) variant. If you add a stock count of 10 to the 2+, and 5 to the 3+, you are telling Shopify you have 30 on hand; 10 on each.
How does inventory get adjusted when purchasing a Quantity Break variant? When?
Inventory is still tracked, but it’s not the usual way you might expect. After the sale (usually between 5-15 minutes after purchase), the Quantity Breaks app will do some magic and update the base variant stock.
Using the same scenario, when a customer buys 5 items, it is the 3+ variant of the product that is actually being purchased. Shortly after, the main (1+) variant stock will be adjusted from 10 down to 5.
The item has been oversold! How did that happen?
There is always the potential for an item to be oversold, but should only happen once. When a product with Quantity Breaks applied to it is purchased, it is the Quantity Break variant being purchased. Inventory is not directly applied on these variants (N/A to Shopify means that it is always available). After the sale, the main variant stock is reduced. If that stock reaches 0 or less, all the Quantity Break variants stock values from N/A to 0. This restricts any more products to be oversold.
Because the app variants are always created with a quantity of "N/A", you will need to press this button if the regular version of the variant already has an inventory of 0 to prevent over selling. Because the app variants are recreated whenever a Quantity Breaks Group is changed, it's good practice to click the sync button after a new group is created or when an existing one is edited.
I cancelled the order. Why didn’t the inventory update?
When a Quantity Break variant is purchased, the app can ‘listen’ to see if it is a Quantity Break variant and reduce the stock. When an order is cancelled, we don’t have the same capability. When cancelling the order, the stock will be returned to the Quantity Break variant, which often will be N/A. The only workaround here is to manually add the inventory back to the main variant.