Closing PO Lines at year-end

 We have numerous purchase orders that cross fiscal years.  Our Procurement group typically just adds a line item to an existing PO for the follow-on year.  Therefore…every year we have a growing list of old project/task numbers showing up on the open PO report.  This means that our BSAs have to put a lot of work into cleaning up old POs and deobligate funds, etc.  Should we be able to close PO lines when the new lines with the new project/task is added?   Is there is a better way to do this?