Which term describes a fixed percentage added to the base rate for determining the APY?

The term that describes a fixed percentage added to the base rate for determining the Annual Percentage Yield (APY) is known as the margin. In the context of calculating APY, the margin acts as an adjustment factor that is added to the base interest rate. This can occur in various financial products, such as Certificates of Deposit (CDs) or adjustable-rate accounts, where the interest rate can vary based on market conditions or specific terms set by the financial institution.

Understanding the role of the margin is critical for consumers as it directly influences how interest will be accrued on their savings. By clearly defining the margin along with the base rate, financial institutions help consumers understand the potential yield they can expect on their deposits.

The other terms do not fit this specific context: a tier typically refers to different levels of rates based on the balance in the account, a rate is a more general term that could refer to the overall interest rate itself, and a bonus usually indicates a one-time additional benefit rather than a fixed percentage adjustment to the base rate.