Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. Here's the information you'll need to have handy to complete your secured promissory note, interest-only with balloon final payment.A single final balloon payment for the entire outstanding Principal amount and interest accrued will be paid on or before the day of. A promissory note is a legal document specifying a contract's terms. Promissory notes, however, can be invalidated in court under certain circumstances. Borrowers will pay this loan as follows: 1. Periodicity (check one):. A straight note is a written document that outlines the terms of a loan agreement between a borrower and a lender.