How to prevent mixing pre-order and in-stock items in a Shopify cart

Short answer: Require pre-order items to be checked out separately so in-stock items aren't held back waiting for pre-order stock. In Checkpost, choose “Don't mix pre-orders with in-stock items” from Templates, adjust the values, test it, then save and enable the rule.

The problem

When a cart mixes pre-order and in-stock items, you either hold the in-stock items until the pre-order arrives or split shipments at your own cost.

How to set it up

1. Install Checkpost from the Shopify App Store.
2. Open Templates and choose Don't mix pre-orders with in-stock items.
3. Tag pre-order products with "preorder".
4. Use Try this rule to test a sample cart, then click Save rule.

The rule

Checkout is blocked when all of these conditions are true:

• Cart contains products tagged preorder
• Cart contains items other than products tagged preorder

Shoppers see: “Pre-order items must be purchased separately from in-stock items.” at the top of checkout, in the cart and at checkout.

{
  "name": "Pre-orders checked out separately",
  "match": "all",
  "conditions": [
    {
      "kind": "cart_contains",
      "filter": {
        "productTags": [
          "preorder"
        ]
      }
    },
    {
      "kind": "cart_contains_other_than",
      "filter": {
        "productTags": [
          "preorder"
        ]
      }
    }
  ],
  "message": "Pre-order items must be purchased separately from in-stock items.",
  "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

• Tag pre-order products (preorder) and remove the tag when stock arrives.
• Explain in the message that in-stock items can be bought in a separate order.

FAQ

Can a cart contain several pre-order items?

Yes. Only mixing pre-order with non-pre-order items is blocked.

Does it work with pre-order apps?

Yes, as long as pre-order products carry a tag your rule can check.

Related rules

Add don't mix pre-orders with in-stock items to your store