An annuity due is a type of annuity where payments are made at the beginning of each period instead of at the end. Examples of annuity due payments include rent, leases, and insurance payments, which are made to cover services provided in the period following the payment. The key difference between an annuity due and an ordinary annuity is that payments for an ordinary annuity are made at the end of the period, while annuity due payments are made at the start of each period/interval. The present value of an annuity due is higher than that of an ordinary annuity by a factor of one plus the periodic interest rate, and the future value of an annuity due is also higher than that of an ordinary annuity by a factor of one plus the periodic interest rate. Annuity due calculations involve adjusting the formulas used for regular annuities to account for the difference in timing, typically by multiplying the familiar annuity formula by (1 + r), where r is the interest rate.