Hi,

I am struggling with a formula to calculate the future value of an annuity.

I have an annual contribution (USD 30.000) which I'd like to know the future value of in 40 years. The annual interest rate is 2.5%.

Each year, a fee (0,2%) must be subtracted from the balance at the end of that year, which is simple enough.

However, the problem is that the fee is kinked, that is, the fee will be 0,2% of the first USD 500,000 of savings, but only 0,1% of anything above USD 500,000.

The formula I have been using so far is Formula.png. To account for the fee, I currently subtract the 0,2% annual fee from the 2,5% annual interest rate, but, I do not know how to adjust the formula for the kink.

I have enclosed a sample workbook. Any help is greatly appreciated.

Thanks,

Phill

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