When filtering the list of timesheets accessed via Placements ; Timesheets Manager using the preset filter Ready for Billing with Errors, the timesheets that appear meet the following criteria which effectively puts them into an 'error' condition. They will need to be remedied before you are able to invoice them:
The timesheet is marked as Ready for Billing, AND
There IS a blank Charge Unit in the placement, OR
There IS a blank Invoice Frequency in the placement, OR
There IS an expense in the timesheet with an approval status other than Approved or REJECTED, OR
There AREN'T any hours worked on the timesheet