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Identify the letter as your final demand. Explain late fees. Give a deadline. Conclude your letter. Mail the letter.
Set up the letter as a standard business letter. However, also include a heading, such as the words "Final Demand." Put the words in bold and underline them. You want the recipient to know that this is their last chance to pay up before you take additional action. You should tell the customer that they are now in breach of your agreement and that you have added interest or a penalty for being late. Then tell them the new total amount they need to pay. Sample language could read: "Despite previous reminders, your account remains delinquent. Because you are now in breach of our payment terms, we are adding a $50 late payment penalty per our 'Late Payment of Debts Terms of Agreement.' The total outstanding debt is now $225.00." You should tell the customer how much time they have to make final payment. You should not give them too much time. For example, you could set a 72-hour deadline. Explain what will happen if the customer doesn't meet the deadline. For example, you might pass the account onto collections or sue the customer in court. Sample language could read: "It is now crucial that you pay your outstanding bill in full within the next seventy-two hours. If you don't, then we will have little choice but to pass this account to our debt collection agency, who will add more charges to the account." You can bold the "seventy-two hours" to make those words stand out. Emphasize that the client should take this final demand letter seriously and pay up. For example, you could write, "We therefore suggest that you take this matter seriously and pay your balance in full as soon as possible." You should send this one through the post, using certified mail, return receipt requested. If you don't hear back from the customer, then go ahead and send the account to collections or suewhichever you threatened in the letter.