When a customer or client has repeatedly failed to bring an account up to date, in other words failed to make payments that are due, it may be necessary to make a final demand for payment. At the same time it might be in the best interest of both parties to try and maintain the relationship, therefore a non-confrontational final demand might be the best option.
Use this document to make a final demand for payment in a non-confrontational manner, but let the customer know that the account is seriously delinquent and that action will be taken if the account is not brought up-to-date. Note that by providing a 10-day notice, as this letter does, the company obligates itself to take action after 10 days. Failure to do so will send the message that you're not to be taken seriously on this matter, and further collection efforts will be even more difficult.