If you want your invoices to display Prices Including VAT to your customers, you need to activate the functionality.
Under Settings - Sales Order/Purchase Order/Invoicing - Invoice Input view you will find the check box Show prices inclusive VAT.
The check box is also available directly on the new Invoice/Order/Quote. See below.
The setting is also available on each customer under Registry - Customers - (Select customer) - Additional Information. This way you can turn on the functionality for certain customers in particular.
The invoices’ total is shown inclusive of VAT regardless of the box being checked or not.