"LeeB" wrote:
What function do I use to calculate the payout (or future value) of a
Certificate of Deposit?

You need to look at the details of the CD disclosure statement to see how
interest is computed. There are several methods in practice.

If interest is compounded daily, the future value of the CD can be computed
by:

=fv(rate/365, daysHeld, 0, -deposit)

where "rate" is the interest rate, not the APY, and "daysHeld" is computed
by subtracting the date of deposit from the date of maturity.

I want to reiterate the fact that not all CDs work this way. Some CDs
compute simple interest on the balance, reinvesting the accumulated interest
periodically (weekly, monthly or quarterly).

Even "daysHeld" is not determined in a uniform manner. For example, some
"9-month" CDs mature in 270 days. Some CDs mature on the anniversary date 9
months late; for example, a 10/1/2005 CD maturing on 7/1/2006 -- 273 days.