Stop the orders you can't fulfil, right at checkout.
Checkpost adds checkout rules to Shopify: block PO Boxes, limit quantities, set order minimums, restrict products by customer, country or state, and stop fraud — enforced inside checkout, including Shop Pay.
Install on ShopifyFree plan available
What you can enforce
Block PO Box addresses
Stop checkout when the shipping address contains a PO Box, so carriers that cannot deliver to PO Boxes never receive the order.
Maximum quantity per product
Cap the quantity of a product per order — perfect for limited drops, launches and high-demand items that resellers target.
Minimum order value
Block checkout until the cart subtotal reaches your minimum, protecting margins on shipping and handling.
Wholesale-only products
Prevent retail customers from buying wholesale SKUs by requiring a wholesale customer tag or a B2B company account.
Restrict products in certain states
Block checkout when a restricted product (for example knives, vapes, supplements or CBD) is shipped to a state or province where it can't be sold.
Stop card-testing bots
Block tiny guest orders — the classic pattern bots use to test stolen card numbers — while logged-in customers shop normally.
Why rules belong in checkout
- Can't be bypassed. Rules run on Shopify's servers, in the cart, at checkout and for Shop Pay, Apple Pay and Google Pay. Cart-drawer scripts can be skipped. Checkout validation can't.
- No theme code. Nothing is injected into your theme, so there's nothing to clean up if you uninstall.
- Explain, don't just refuse. Every rule shows your own message next to the field the shopper needs to fix.
- Test before going live. The built-in simulator shows exactly which rules a sample cart would trigger.
- Fails open. If anything unexpected happens, checkout continues. A rules app should never cost you a sale by accident.
- No customer data stored. Live rules are saved on Shopify; the app stores sessions, rule drafts and recent rule history. Simulator carts are evaluated locally.
Combine any of 38 conditions
Cart: cart subtotal, cart total (incl. tax & shipping), total item quantity, number of different items. Products in cart: cart contains products, cart does not contain products, cart contains other products than, quantity of any single cart line, quantity per product across variants, quantity per variant across cart lines, combined quantity of products, combined subtotal of products. Customer: customer is logged in, customer is a b2b company buyer, customer tags, customer's previous orders, customer's lifetime spend, email address, phone number. Shipping address: has a shipping address, country, state / province, zip / postal code, city, address line 1, address line 2, company, first name, last name. Delivery: delivery method type, delivery method name. Market: market country, storefront language. Date & time: time of day, day of the week, date. Cart attributes: cart attribute, compare two values. Full reference →