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 cognovit promissory note is a legal document that obligates the borrower to repay the lender. There are many types of payment methods. Set loan terms with larger payments at the end. A promissory note can be structured as: (1) Installment Note; (2) Interest Only Note; or (3) Straight Note.