When an order is paid, then an invoice is automatically generated, unless the order is €0 and then there is no invoice created.
The generated invoice can be found under 'My account' (1) -> 'Documents' -> 'Orders' (2)
The details of an invoice are those that are shown in the order details page. To download the actual invoice you have to click document icon (4)
Here you can distinguish five different sections.
On this section, you can find the invoice-specific information, such as invoice number, which is a unique identifier, as well as the document as such, in a PDF format that you can download.
On this section, you can find the personal details of the person to whom the invoice was addressed to, such as name, company name, address and VAT number.
On this section, you can find the shipping information that has been used to send the items of the invoice.
On this section, you can see the payment method that has been used for this order.
On this section, all the items that have been invoiced are shown. If you have paid e.g. two ETS Professional licenses and one ETS App, then you will see that on the first line there is one entry for ETS Professional where the 'Amount' field is two and one entry for the ETS App.