If you have invoices that show up on the aged receivables report, but not in the Reciepts window, chances are it is because the invoice doesn’t have an invoice number assigned.  The obvious solution is to open the invoice in Sales/Invoicing and enter an invoice number or print the invoice.  Once you do this, it will show up in Reciepts so you can apply your customer’s payment.

If the invoice happens to be from a year that has already been closed, you won’t be able save any changes to it.  And you won’t be able to print it from the Sales/Invoicing window.  But here is an alternate method that will work.  This is also helpful if you have a lot of invoices without numbers.  Go to the Reports & Forms menu, choose Forms, then Invoices and Packing Slips.  In the Forms list, select the invoice format you want to print and click the Preview and Print button.  Make sure the Invoice to print/email option is set to Unprinted Invoices.  Click the Refresh List button to see what invoices will be printed.  If there are any invoices listed that you don’t want to print, remove the check mark next to those invoices.  Finally, click the Print/E-Mail button.  After they print, make sure you answer Yes to the question “Did the invoices print and e-mail properly, and is it OK to assign the invoice numbers to the invoices?”