The effective interest rate, effective annual interest rate, annual equivalent rate (AER) or simply effective rate is the
interest rate on a loan or financial product restated from the
nominal interest rate as an interest rate with annual
compound interest payable in arrears. It is used to compare the annual interest between loans with different compounding terms (daily, monthly, annually, or other).
The effective interest rate differs in two important respects from the
annual percentage rate (APR):
1. the effective interest rate generally does not incorporate one-time charges such as front-end fees;
2. the effective interest rate is (generally) not defined by legal or regulatory authorities (as APR is in many jurisdictions).
By contrast, the
effective APR is used as a legal term, where front-fees and other costs can be included, as defined by local law.
Annual percentage yield or effective annual
yield is the analogous concept used for savings or investment products, such as a
certificate of deposit. Since any loan is an investment product for the lender, the terms may be used to apply to the same transaction, depending on the point of view.
Effective annual interest or yield may be calculated or applied differently depending on the circumstances, and the definition should be studied carefully. For example, a
bank may refer to the yield on a loan portfolio after expected losses as its effective yield and include income from other fees, meaning that the interest paid by each borrower may differ substantially from the bank's effective yield.
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In finance and economics nominal interest rate or nominal rate of interest refers to the rate of
interest before adjustment for inflation (in contrast with the
real interest rate); or, for interest rates "as stated" without adjustment for the full effect of
compounding (also referred to as the nominal annual rate). An interest rate is called nominal if the frequency of compounding (e.g. a month) is not identical to the basic time unit (normally a year).