In order to receive invoices, please update your billing address during the checkout process, making sure to input a company name and TAX ID (VAT number). Once you do that, an "I want to receive an invoice" checkbox should appear in the checkout - tick it. Following that, you will be able to generate invoices from your Orders list (https://www.kinguin.net/app/dashboard/expressorders) for the given purchase.
You can follow the steps included in the video tutorial:
If you already made the purchase without following the steps and would like to receive an invoice for it, please contact our support team via a ticket: https://kingu.in/ContactSupport