OK, so you would have to calculate your APY using the following rules:
Variable-rate accounts with an introductory premium (or discount) rate must be calculated like a stepped-rate account. Thus, an institution shall assume that: (1) The introductory interest rate is in effect for the length of time provided for in the deposit contract; and (2) the variable interest rate that would have been in effect when the account is opened or advertised (but for the introductory rate) is in effect for the remainder of the year. If the variable rate is tied to an index, the index-based rate in effect at the time of disclosure must be used for the remainder of the year. If the rate is not tied to an index, the rate in effect for existing consumers holding the same account (who are not receiving the introductory interest rate) must be used for the remainder of the year.
For example, if an institution offers an account on which it pays a 7% interest rate, compounded daily, for the first three months (which, for example, contain 91 days), while the variable interest rate that would have been in effect when the account was opened was 5%, the total interest for a 365-day year for a $1,00 deposit is $56.52 (based on 91 days at 7% followed by 274 days at 5%). Using the simple formula, the annual percentage yield is 5.65%:
APY = 100 (56.52/1,00)
APY = 5.65%
The APYWIN program, as far as I know will not calculate step rate multiple tier accounts when the interest rate reverts to a Tiering Method B formula. You will have to do this manually. So you calculate based on the low and high balance in each tier.
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