How to require quantities in multiples (case packs) on Shopify

Short answer: Only allow quantities in multiples of a pack size — e.g. 6, 12 or 24 — for case-packed goods like wine, beverages or wholesale stock. In Checkpost, choose “Sell in case packs / multiples” from Templates, adjust the values, test it, then save and enable the rule.

The problem

Wine, beverages, eggs and wholesale stock ship in cases. An order for 7 bottles when a case holds 6 means splitting cases, re-packing or a partial shipment.

How to set it up

1. Install Checkpost from the Shopify App Store.
2. Open Templates and choose Sell in case packs / multiples.
3. Set the pack size and choose the products.
4. Use Try this rule to test a sample cart, then click Save rule.

The rule

Checkout is blocked when all of these conditions is true:

• Quantity per variant across cart lines (products tagged case-6) is not a multiple of 6

Shoppers see: “This product is sold in cases of 6. Please adjust the quantity.” at the top of checkout, in the cart and at checkout.

{
  "name": "Case packs of 6",
  "match": "all",
  "conditions": [
    {
      "kind": "line_number",
      "field": "variant_quantity",
      "op": "not_multiple_of",
      "value": 6,
      "filter": {
        "productTags": [
          "case-6"
        ]
      }
    }
  ],
  "message": "This product is sold in cases of 6. Please adjust the quantity.",
  "target": "cart",
  "runOn": "always"
}

Where this rule works

These are cart and checkout validations, including supported accelerated checkouts. They are current-cart policies; they do not track previous purchases of a SKU. Shopify excludes POS, recurring subscription orders and native pre-order/Try Before You Buy flows from this API. See Shopify's validation compatibility.

Tips

• Set the pack size as the value and choose "is not a multiple of".
• If customers can mix flavours within a case, switch to "Combined quantity of products" so the total across all variants must be a multiple.
• Show the pack size on the product page to avoid surprises.

FAQ

Can I sell 6-packs and 12-packs of the same product?

Yes. A multiple of 6 also allows 12, 18 and 24.

Will the quantity be corrected automatically?

No. Checkout rules explain the problem and the shopper adjusts the quantity, so the cart never changes without them knowing.

Related rules

Add sell in case packs / multiples to your store