Using the Collection Manager
Click a column in the graph to see the customers and invoices that make up that column. You can do the same thing in the Numeric display of this data.
Select the check boxes beside those customers to whom you want to send a collection letter; then select the Letter button at the top of the window.
To see just the totals for a single customer, highlight the customer, and click the Source button. To see the original invoice, highlight the transaction, and click the Detail button or just double-click the transaction.