Dear …
RE: __(Loan/Note – Reference Name/Number)__
__(I am/We are)__ are in receipt of your payment of __($amount)__. Thank you. This amount represents payment in full towards the principle amount of your __(loan/note/etc.)__. At this time, __(I/we)__ would like to bring to your attention that the interest, in the amount of __($amount)__, still remains outstanding.
__(Therefore, __(I/we)__ ask that you kindly forward your payment of __($amount)__ to settle up this account in its entirety/However, upon review of the diligence you demonstrated in the repayment of this loan/note, we have made the decision to waive the interest owing.)__. Thank you, __(Name)__, for being assiduous in the settlement of this loan/note. It was a pleasure to have offered you credit.
__(I/We)__ appreciate your valued business, __(name)__, and hope to hear from you soon.
Regards,