( ) INTEREST ONLY PAYMENTS on the outstanding principal balance. (The following must be completed if "b" or "c" is checked).Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. A monthly interest rate can be included on the promissory note. Here's the information you'll need to have handy to complete your secured promissory note, interest-only with balloon final payment. How to Write a Promissory Note in Washington? Interest Only Payments. A balloon note is a type of loan where the borrower is required to make regular payments, called interestonly payments, for a specified period.