The collection letters show only the open amount on the invoice. This is fine, but would be more useful to inform the customer about the status of the invoice. It would be good to note the original amount of the invoice and the sales tax on the invoice. We have a lot of problems with customers shorting the payment by the sales tax amount. Generally, this is just an oversight. If the sales tax were displayed on the collection letter it would be a clue to the customer way the invoice is still open.