Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. Promissory note is the written contract between the borrower and the lender that is the promise to repay the debt including interest payments.Set loan terms with larger payments at the end. A single final balloon payment for the entire outstanding Principal amount and interest accrued will be paid on or before the day of. A balloon payment is a larger than current one time payment at the close of the loan term.