That are Two methods like :-
Method 1
:- you want to remove using css try this code your custom css file.
.checkout-index-index .payment-option._collapsible.opc-payment-additional.discount-code {
display: none;
}
Method 2
:- you don't want to hide discount code using css. So try you xml file way
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="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">
<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>
After you change run some basic command :-
php bin/magento c:c
php bin/magento c:f
you want to get more information :-
How can i hide Discount Code form checkout payment page in Magento 2?
THANKS.