In the Shop Checkout template the coupon field appears on the right sidebar.
This coupon field can be deactivated or made collapsible from the Customizer settings.
For the other templates, there's no coupon field in the Customizer- you can only add it/make it collapsible through the Fields tab outside.
Let's look at how to deactivate the coupon field in the Shop Checkout template.
Step 1: Click on the 'Edit' button to open the ShopCheckout template in Customizer
The Customizer will open up.
Step 2: Click on the Your Cart widget from the left side panel in Customizer
Next, scroll down to the Coupon section.
Step 3: Choose to hide the coupon field or make it collapsible
In the Coupon section, you'll find the option to hide the coupon field from the sidebar or make it collapsible.
Take a look:
Select the option as per your requirements.
Alternatively, you can click on the pencil icon next to the checkout form and scroll below to find the mini cart-related options.
Step 4: Hit the 'Publish' button to save your changes
There you go! Now you can preview the checkout page to see the changes you made.