To view your invoices (the ones that have already been billed, not the drafts); go to Invoicing > Invoices. 

Use the list view dropdown on the left or the filters on the right if you do not see your desired invoice at first glance. You can also use the search box at the top; next to the Operate logo, to search for information that might relate to your invoice.

TIP: If you have the invoice number, enter it in the Search box to find your invoice faster.

Once you find the invoice you need, click the invoice number to view more details.

Preview invoices either from the detail page (use the Preview button on the right); or from within the invoice list (select your invoice and click Preview above)

Use the Export button above the list to export your selected invoices to be able to use them with other applications.

Reset selected invoices if needed - please note that resetting invoices might lead to gaps in invoice numbers.

Unbook selected invoices as needed - This cancels / voids the selected invoice. Invoices are unbooked until they are exported - then the status will be changed to Booked. The Unbook feature should be used sparingly and with strong user controls.