The monthly Interest Cost represents the interest expense on the Public Debt Outstanding as of each month end. The interest expense on the Public Debt includes interest for Treasury notes and bonds; foreign and domestic series certificates of indebtedness, notes and bonds; Savings Bonds; as well as Government Account Series (GAS), State and Local Government series (SLGs), and other special purpose securities. Amortized discount or premium on bills, notes and bonds is also included in interest cost.
The fiscal year Interest Cost represents the total interest expense on the Public Debt Outstanding for a given fiscal year. This includes the months of October through September.