What is the difference between a tax invoice and a simplified invoice?

• Tax invoice: for a company customer with a VAT number. It needs the customer's full details (VAT number and national address), and ZATCA clears it before it is given to the customer.
• Simplified invoice: for an individual or a company without a VAT number, including POS sales. It prints at once, and the system reports it to ZATCA within minutes.

You don't choose the type: the system decides it — a customer with a VAT number gets a tax invoice.