The Invoice Grouping setting within the Client Entry record determines how the system will collate timesheets for invoicing for this client:
If set to candidate as in the example above all timesheets that have been validated for billing will move into the Create Sales Invoice area ready to be invoiced and you will see the system is set to separate these by candidate:
If we click the Items link shown above we can see that in this example we have three timesheets to be billed, two of them for the same candidate for different period and the third timesheet for another candidate:
If we produce the invoice in the normal way from the previous screen the result would be two invoices - one detailing the two timesheets for the same candidate with the other candidate on the other invoice:
If however on the Create Sales Invoice screen you click into the Items link you will be able to override this setting if you wish by selecting timesheets and instructing the system to invoice as per your selection.
Other options within the Invoice Grouping setting are Timesheet which means a separate will be raised per timesheet, Purchase Order will be collate timesheets based on their PO, Client where all timesheets, regardless of period or candidate, will be placed together on one consolidated invoice, and finally Manual/Self Bill where the system will not auto-compile them at all, but will wait for you in instruct it on which timesheets you wish to appear on each invoice (you do this by clicking the Timesheet link on the Create Sales Invoice area).