specific custom field in checkout opencart 3.0.3

I am looking for a solution to create in the checkout of Opencart 3.0.3 a custom field of the type "I want the invoice" with double checkbox o radio buttons Yes / No, and therefore the customer every time he makes an order he can choose if he wants the invoice or not, and I can see that information in the order confirmation email that arrives to the Administrator.
Thanks for any suggestions

It is not possible to achieve using custom fields as these fields do not show up unless the customer adds a new address.
You can check this module. It allows the customer to choose optional offers either free or paid. You can create a free offer https://www.opencart.com/index.php?rout ... n_id=14144

If you can't find an extension, you could pay a developer such as ourselves or post a job in the Commercial Support Forum.