Magento2 Hide Discount Code form Cart and Checkout Page

the best way is to work on your custom theme by modifying these files

/app/design/frontend/{Vendor}/{theme}/Magento_Checkout/layout/checkout_index_index.xml

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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="component" xsi:type="string">uiComponent</item>
                                            <item name="children" xsi:type="array">
                                                <item name="payment" xsi:type="array">
                                                    <item name="children" xsi:type="array">
                                                        <item name="afterMethods" xsi:type="array">
                                                            <item name="children" xsi:type="array">
                                                                <!--Disable Discount here-->
                                                                <item name="discount" xsi:type="array">
                                                                    <item name="config" xsi:type="array">
                                                                        <item name="componentDisabled" xsi:type="boolean">true</item>
                                                                    </item>
                                                                </item>
                                                            </item>
                                                        </item>
                                                    </item>
                                                </item>
                                            </item>
                                        </item>
                                    </item>
                                </item>
                            </item>
                        </item>
                    </item>
                </argument>
            </arguments>
        </referenceBlock>
    </body>
</page>

 

/app/design/frontend/{Vendor}/{theme}/Magento_Checkout/layout/checkout_cart_index.xml

 

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<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.cart.coupon" remove="true"/>
    </body>
</page>