- To enable the invoices automatic generation, enable the developer
  mode, go to Settings \> Automation \> Scheduled Actions
- Filter the archived actions and activate 'Generate Standard Invoices'.
- Adapt the frequency you want to automatically generate invoices to
  your needs.
- The field 'Next Invoice Date' on partner form indicates when the next
  invoice generation will take place.
- To manually change the invoicing group (one invoice per order), go to
  the Sale Order \> Other Information \> Invoicing and Payments and
  check the 'One Invoice Per Order' box.