Professional Header. A debt collection letter informs clients about their unpaid bills.Today's Date: Collector's Name: Collector's Address : RE: Account of. A debt collector is required to send you a written notice within five days after you are first contacted, telling you the amount of money you owe. A good first step is to write a short letter to the customer, explaining that you are attempting to collect on a debt. Relating to the debt. I respectfully request that your offices provide me with competent evidence that I have any legal obligation to pay you. Send this letter as soon as you can -- if at all possible, within 30 days of when a debt collector contacts you the first time about a debt. This establishes the official timeline of your correspondence, which can be crucial for legal purposes. Fortunately for consumers, judgments do not renew automatically.