Fixed income refers to any type of investment that yields a regular (or fixed) return.

For example, if you lend money to a borrower and the borrower has to pay interest once a month, you have been issued a fixed-income security. When a company does this, it is often called a bond or corporate bank debt (although 'preferred stock' is also sometimes considered to be fixed income). Sometimes people misspeak when they talk about fixed income. Bonds actually have higher risk, while notes and bills have less risk because these are issued by government agencies.

The term fixed income is also applied to a person's income that does not vary with each period. This can include income derived from fixed-income investments such as bonds and preferred stocks or pensions that guarantee a fixed income. When pensioners or retirees are dependent on their pension as their dominant source of income, the term "fixed income" can also carry the implication that they have relatively limited discretionary income or have little financial freedom to make large expenditures.

Fixed-income securities can be contrasted with variable return securities such as stocks. To understand the difference between stocks and bonds, you have to understand a company's motivation. A company wants to raise money, and it doesn't want to wait until it has earned enough through ongoing operations (selling products or providing services). In order for a company to grow as a business, it often must raise money; to finance an acquisition, buy equipment or land or invest in new product development. Investors will only give money to the company if they believe that they will be given something in return commensurate with the risk profile of the company. The company can either pledge a part of itself, by giving equity in the company (stock), or the company can give a promise to pay regular interest and repay principal on the loan (bond) (bank loan) or (preferred stock).

While a bond is simply a promise to pay interest on borrowed money, there is some important terminology used by the fixed-income industry:

• The issuer is the entity (company or govt.) who borrows an amount of money (issuing the bond) and pays the interest.
• The principal (of a bond) is the amount that the issuer borrows.
• The coupon (of a bond) is the interest that the issuer must pay.
• The maturity is the end of the bond, the date that the issuer must return the principal.
• The issue is another term for the bond itself.
• The indenture is the contract that states all of the terms of the bond.

People who invest in fixed-income securities are typically looking for a constant and secure return on their investment. For example, a retired person might like to receive a regular dependable payment to live on, but not consume principal. This person can buy a bond with their money, and use the coupon payment (the interest) as that regular dependable payment. When the bond matures or is refinanced, the person will have their money returned to them.