A series of equal payments at equal intervals. The modifiers commonly used with the term "annuity" indicate the value of the annuity at a particular date relative to the cash flows. For example, the "present value / net present value of an annuity" refers to the value of an annuity at a date one payment period before the date of the first payment. The "present value / net present value of an annuity due" refers to the annuity value at the date of the first payment. TValue handles these relationships automatically based on the dates you enter.