# Order validation apps: block checkout when your rules fail

ORDER VALIDATION APPS: BLOCK CHECKOUT WHEN YOUR RULES FAIL

Some apps in the LaunchMyStore marketplace use order validation to stop orders
that violate your business rules — minimum order amounts, restricted countries,
banned product combinations, age-restricted goods. This article explains what to
expect when you install one.


WHAT IT DOES

An order validation app inspects the cart, customer, and shipping address when
the shopper clicks Place order. If the app returns one or more errors, the order
is rejected and the shopper sees an explanation. If it returns nothing, the
order proceeds normally.

Validation runs only at the moment of placement — not on the cart or earlier
checkout steps — so the rule is enforced regardless of how the shopper navigated
through your store.


EXAMPLES

 * Enforce minimum order amounts: "Orders under $25 cannot be placed" to limit
   losses from card-processing fees on tiny baskets.
 * Restrict shipping countries: "We don't ship to country X right now — please
   contact us".
 * Block restricted combinations: "This same-day item can't ship with a
   special-order item that takes 2 weeks".
 * Per-line quantity caps: "Maximum 10 units of '<product>' per order".
 * Guest-checkout cap: "Orders over $500 require an account — please sign in to
   continue".
 * Region-locked products: "This item can only ship to addresses in the EU".


WHAT YOU'LL SEE

When validation fails, the checkout shows an inline error banner above the
place-order button, using the message the app supplied. The order is not
created, and the shopper can adjust their cart or address and try again.

Choose apps that return clear, actionable error messages ("Reduce the quantity
from 15 to 10") rather than cryptic codes — the wording shoppers see comes
directly from the app.


INSTALLING AN APP THAT USES THIS

 1. Open Apps → Marketplace in your admin.
 2. Browse order-management or compliance apps and open one that fits your need.
 3. Review the permissions and click Install.
 4. Configure the rules (thresholds, blocked countries, SKU lists) in the app's
    settings.
 5. Test both paths — an order that should pass and one that should be blocked —
    before going live.


LIMITS AND TIPS

 * You can have up to 5 order validation apps active at once. They all run on
   every order placement; if any one returns an error, the order is blocked.
   Errors are combined and shown together.
 * Always test the blocking path. A misconfigured rule can silently block valid
   orders — run a known-bad cart through checkout to confirm the right error
   appears for the right reason.
 * Validation only blocks; it can't change the cart. For soft warnings ("Heads
   up: this product takes 2 weeks to ship"), you need a different kind of
   extension — pair them if you want both a warning earlier and a hard block at
   placement.
 * If a validation app fails or times out, it's skipped for that order rather
   than blocking commerce. The other validation apps still run, so misbehaving
   apps don't take down checkout.
 * The shopper can't override the block. Validation errors are hard stops at the
   place-order step; if you want a request-an-exception flow, you need an app
   that ships its own form.
 * Removing the app removes the rules. Existing orders are untouched; new orders
   go back to standard validation.


FOR DEVELOPERS

If you want to build an app that uses an order validation function, see the
developer documentation at docs.launchmystore.io
[https://docs.launchmystore.io].