There are many ways of doing this, but you need to be more specific? Do you extract the data from the ledger, and is there a flag identifying paid from unpaid?
If you had a list of unpaid invoices with e.g. a due date, you could for instance create a pivot table (Data -> Pivot Table Wizard) which summarises them in chronological order. Alternatively you could sort the list by due date (Data -> Sort).
I have a spreadsheet with worksheets for 12 mths of financial year. We run invoices from this using macro exporting to word. we enter amount due tax etc, we also put in daye of invoice and when payment due. Currently we identify overdue invoices by noting blank spaces in payment received date column.
Invoice No Client Address 1 Address 2 Address 3 Address 4 Postcode Contact Accounts Contact Job Title Candidate Salary Rate % Amount Invoiced VAT Total inc VAT Start Date Date Invoiced Payment Due Date Actual Payment Date Days Overdue