#USNationalDebt The US national debt is the amount of money the federal government has borrowed to cover the outstanding balance of expenses incurred over time. In a given fiscal year (FY), when spending (ex. money for roadways) exceeds revenue (ex. money from federal income tax), a budget deficit results. To pay for this deficit, the federal government borrows money by selling marketable securities such as Treasury bonds, bills, notes, floating rate notes, and Treasury inflation-protected securities (TIPS). The national debt is the accumulation of this borrowing along with associated interest owed to the investors who purchased these securities. As the federal government experiences reoccurring deficits, which is common, the national debt grows.