Interest is the cost of using money. The interest rate paid is usually expressed in annual terms though money market instruments may have a shorter term than one year. An interest rate is determined by dividing the amount of interest paid by the principal amount borrowed. For example, if a $1000 bond pays $85 in interest for one year, the annual interest rate is 8.5 percent. In the U.S. some interest-bearing bonds, such as municipals, entitle the bearer to an exemption from certain taxes on interest income. The interest paid by a company on its outstanding debt as well as the interest paid by a homeowner on his/her mortgage, is deductible from income as an expense and so can reduce the amount of tax owed.

利息是使用货币的成本。利率的支付形式通常以年为期限，虽然金融市场票据会有一个更短的时间。利率的制定取决于借款本金所划分的利息。举个例子，如果1,000美元的债券每年支付85美元的利息，那么年利率就是8.5%。美国有一些有息债券，如政府债券，它允许持有人在利息收益上有一定的免税。公司未偿债务和按揭住房的屋主需支付的利息可以作为一项费用减少他们的应交税金