Rules: payment, shipping, validation and cart links

Applies to: TreStack Checkout, every plan
Updated: 17 October 2026

Rules change how Shopify's checkout behaves. They run as Shopify Functions, so nothing needs to be placed in the checkout editor. Available on every plan. Open Rules & Customizations in the app's menu, then Payment methods, Shipping options, Order validation or Cart links.

Every rule has a name (buyers do not see it), a Status of Active or Draft, and optional conditions. Without conditions, a rule always applies.

Conditions

Conditions are grouped. Within a group choose All conditions must match (AND) or Any condition can match (OR); between groups choose Any group can pass or All groups must pass. Condition types differ by rule; examples are Cart Total, Product, Product is in Collection, Shipping Country and Customer Tag.

Some condition types can only be combined with others from the same set. If a rule shows Condition types are locked for this customization (or for this validation), create a new rule for the other set.

Payment methods

On Payment methods, choose Create rule, then under What should the rule do? pick:

• Hide Payment Method, for example cash on delivery on large orders;
• Change Name of Payment Method;
• Reorder Payment Method.

Choose methods in Select Payment Method. If yours is not listed, type its name and press Enter.

Shipping options

On Shipping options, choose Create rule, then pick:

• Hide Shipping Method;
• Add Message to Shipping Method or Change Shipping Method Name;
• Reorder Shipping Method.

A method matches Partial (part of the name, recommended) or Exact. When reordering, Shopify requires the lowest priced shipping option to stay at the top.

Order validation

On Order validation, choose Create validation. A validation stops checkout when its conditions match, for example a P.O. Box address.

• Error Message is what the buyer sees; Error Message Location puts it at the top of checkout or next to a field.
• Run Location: Checkout Completion (when the buyer selects Pay now), Checkout Interaction (while they fill in fields), or both.

Names and messages can be translated with Show Translations (Optional).

Cart links

On Cart links, choose Create cart link to build a link that fills the cart and sends the buyer to checkout.

• Link: pick the Store domain and type a Link name.
• Products: choose Add product and set quantities.
• Checkout information (optional): the buyer's email, a shipping address and an Order note.
• Link options (optional): Redirect to cart instead of checkout and a Discount code.
• Choose Save link. Copy it under Your link, or from the list, with Copy link.

If Shopify refuses a rule, Home shows A customization is not live on your checkout. Open the rule and save it again.