How to export data relevant for invoicing?

Data can be exported to excel to create an accurate invoice to customers, as well as an invoice attachment as proof to customers of the services provided. Export is done from the Timesheets section:

Export to Excel

All data for a given period is exported to excel. After that, in Excel it is very easy to filter the selected client for whom the invoice is made, where data on all types of work done for that client are displayed, as the number of hours spent with an indication of what is billable and non-billable.

Export by client