Magento 2: How to Add Custom Validations Before Order Placement

Learn how to implement custom checkout validations in Magento 2 before an order is placed. This approach allows you to validate custom business rules, restrict checkout under specific conditions, and improve order processing workflows.

Overview

Magento 2 provides an additional payment validator mechanism that allows developers to execute custom validation logic before the order is placed. Using this approach, you can prevent checkout completion based on custom business requirements such as customer restrictions, order limits, product conditions, shipping requirements, or any custom validation rules.

Step 1: Create checkout_index_index.xml File

Create the following layout file:

app/code/Vendor/Extension/view/frontend/layout/checkout_index_index.xml 
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      layout="1column"
      xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <referenceBlock name="checkout.root">
            <arguments>
                <argument name="jsLayout" xsi:type="array">
                    <item name="components" xsi:type="array">
                        <item name="checkout" xsi:type="array">
                            <item name="children" xsi:type="array">
                                <item name="steps" xsi:type="array">
                                    <item name="children" xsi:type="array">
                                        <item name="billing-step" xsi:type="array">
                                            <item name="children" xsi:type="array">
                                                <item name="payment" xsi:type="array">
                                                    <item name="children" xsi:type="array">
                                                        <item name="additional-payment-validators" xsi:type="array">
                                                            <item name="children" xsi:type="array">
                                                                <item name="orderValidation" xsi:type="array">
                                                                    <item name="component" xsi:type="string">
                                                                        Vendor_Extension/js/view/validate
                                                                    </item>
                                                                </item>
                                                            </item>
                                                        </item>
                                                    </item>
                                                </item>
                                            </item>
                                        </item>
                                    </item>
                                </item>
                            </item>
                        </item>
                    </item>
                </argument>
            </arguments>
        </referenceBlock>
    </body>
</page>

This layout file registers your custom validator component within Magento's additional payment validators system.

Step 2: Create validate.js Component

Create the following JavaScript component to register the custom validator.

app/code/Vendor/Extension/view/frontend/web/js/view/validate.js 
define(
    [
        'uiComponent',
        'Magento_Checkout/js/model/payment/additional-validators',
        'Vendor_Extension/js/model/validate'
    ],
    function (Component, additionalValidators, orderCustomValidation) {
        'use strict';

        additionalValidators.registerValidator(
            orderCustomValidation
        );

        return Component.extend({});
    }
);

This component registers your custom validator with Magento's checkout validation framework.

Step 3: Create Custom Validation Logic

Create the validator file that contains your custom order restriction logic.

app/code/Vendor/Extension/view/frontend/web/js/model/validate.js 
define(
    [
        'jquery',
        'Magento_Ui/js/modal/modal',
        'mage/url',
        'mage/validation'
    ],
    function ($, modal, url) {
        'use strict';

        return {
            validate: function () {

                var order = false;

                // return true if order success

                // return false if restrict order

                // Add your custom validation logic here

                return order;
            }
        };
    }
);

Inside the validate() method, implement your custom validation rules. Return true to allow order placement and false to prevent the order from being submitted.

Step 4: Run Magento Commands

Execute the following Magento commands: 

php bin/magento setup:upgrade

php bin/magento setup:static-content:deploy -f

php bin/magento cache:flush

Result

After implementing this customization, you can:

  • Add custom checkout validation rules.
  • Restrict order placement based on business logic.
  • Validate customer, cart, or product conditions.
  • Prevent invalid orders before submission.
  • Enhance checkout control without modifying Magento core files.