Background I’ve been taking this online course in corporate finance lately, and I figured I’d share some of my knowledge I’ve learned in my recent fixed income securities module. Fixed Income Securities You’ve probably heard of fixed income securities⸺things like bills, notes, and bonds. When they’re issued by the U.S. government, they’re considered about as safe as it gets, because, well, the U.S. has never defaulted on its debt. Think of a fixed income security as a formal IOU.