1234, Main Street
Boston, MA 02123
04 April, 2005
<Recipient Address Goes Here>
Re: Account No. <account number>
This is to inform you that the above-mentioned account is now seriously past due.
The last payment was due in the amount of [$ ??] on [date]. We have not received any payment since your last billing period.
In case you have made the payment, please accept ignore this mail. However, if the payment has not been made, please arrange your payment at the earliest to prevent this account from becoming delinquent.
Thank you for your attention to this matter.
encl: <List of enclosed items goes here>