How to sell mixed cases of 6 across Shopify products and variants

Short answer: Require the combined quantity of products tagged case-6 to be a multiple of 6, so customers can build a mixed case without buying 6 of each flavour. In Checkpost, choose “Mix-and-match cases of 6” from Templates, adjust the values, test it, then save and enable the rule.

The problem

Mixed-flavour cases need one combined pack total. Requiring six of every flavour prevents a legitimate three-plus-three order. This preset treats the tagged set as one case pool, rather than applying the increment to each SKU.

Related merchant discussion on Shopify Community

How to set it up

1. Install Checkpost from the Shopify App Store.
2. Open Templates and choose Mix-and-match cases of 6.
3. Tag every eligible flavour or product and set the case size. Use per-variant case packs when every SKU must fill its own case.
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:

• Combined quantity of products (products tagged case-6) is not a multiple of 6

Shoppers see: “Build a full mixed case: choose 6, 12 or 18 qualifying items in total.” at the top of checkout, in the cart and at checkout.

{
  "name": "Mixed cases of 6",
  "match": "all",
  "conditions": [
    {
      "kind": "line_number",
      "field": "matching_quantity",
      "op": "not_multiple_of",
      "value": 6,
      "filter": {
        "productTags": [
          "case-6"
        ]
      }
    }
  ],
  "message": "Build a full mixed case: choose 6, 12 or 18 qualifying items in total.",
  "target": "cart",
  "runOn": "always"
}

Examples with the default settings

These outcomes apply to this rule alone. Other enabled rules may also affect checkout.

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

• Tag every eligible flavour case-6, including flavours sold as separate products.
• Keep all eligible products under the same pack-size policy; a case of 6 and a case of 12 need separate tags and rules.
• It validates quantities; it does not create a bundle price, discount or packaging line.

FAQ

Can shoppers buy three of two different flavours?

Yes: 3 + 3 fills one case of 6. The default also permits 12, 18 and other whole-case totals.

Can non-case products fill the remaining slots?

No. Only quantities belonging to products tagged case-6 count.

Related rules

Add mix-and-match cases of 6 to your store