Reminder about unpaid installment [Date] [Name] [Address] Dear [Name] We write to inform you that [Number] installment of [Amount] was not made on [Date]. Can we remind you of our letter of [Date], in which we clearly state that the matter would be referred to our legal representatives in event of a missed payment. Can you give this matter your prompt attention. We look forward to receiving your payment no later than [Date]. Yours Sincerely [Your Name] [Your Title]