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Validation Rules ​

Block checkout and show customers a clear, helpful message when their order doesn't meet your requirements.

What validation rules do ​

A validation rule stops a customer from completing checkout and shows a custom error message. The customer must fix the issue before proceeding.

This is different from discounts or payment/delivery rules — validation rules are blockers, not modifications.

Common use cases ​

Wholesale minimum order

  • Condition: Customer tag = wholesale AND Cart total < $50
  • Action: Show error "Wholesale orders require a $50 minimum. Please add more items."
  • Result: Wholesale customers who haven't reached the minimum see the message and can't proceed

Prevent back-order combinations

  • Condition: Cart contains product BACKORDERED-SKU
  • Action: Show error "This item is currently on backorder. Please remove it to continue."
  • Result: Orders with out-of-stock items are blocked cleanly

Maximum quantity limit

  • Condition: Item count > 50
  • Action: Show error "Orders are limited to 50 items. Please split your order."
  • Result: Unusually large carts are blocked

B2B-only product protection

  • Condition: Product in cart = B2B-ITEM AND Customer tag ≠ b2b
  • Action: Show error "This product is available to business customers only. Contact us to apply."
  • Result: Retail customers can't purchase B2B-restricted products

Setting up a validation rule ​

  1. New Rule → Validation
  2. Add conditions — think about exactly when the block should trigger
  3. Write your error message (customer-facing, keep it helpful and actionable)
  4. Name the rule and click Activate

Writing a good error message ​

Your error message appears directly in the customer's checkout. Best practices:

  • Explain the problem: "Wholesale orders require a $50 minimum"
  • Tell them what to do: "Please add more items to continue"
  • Avoid technical language: No internal rule names or codes
  • Be concise: 1–2 sentences is enough

Testing validation rules ​

Before activating, use the Rule Playground in CheckoutMate to simulate the rule with different cart configurations. Note that the playground is a client-side simulation — actual Shopify checkout behavior may differ in edge cases. Always test in an incognito window after activating.

Always test with an incognito window after activating to confirm the error message appears correctly.