Many times subcontractors are not paying attention to what period they are entering their billing under and just selecting the first one that pops up. Which could result in a Subcontractor creating a billing in a period that has expired. This is happening quite often. The only way to fix this is to delete the billing from the older period and re-enter to the correct period.
The ability as a project administrator to move the Subcontractor billing to the correct period without having to delete it and re-enter it would be very useful.