How to age your receivables
For each open invoice, compare the due date with the report date. Not yet due goes in Current; otherwise put the balance in 1-30, 31-60, 61-90 or Over 90 days past due. The share-of-total row shows how much of what you are owed is getting old.
Work the oldest buckets first: the longer an invoice is overdue, the less likely it is to be paid.