What method is used to determine taxable portion of each annuity payment?

The taxable portion of each annuity payment is typically determined using the "exclusion ratio." This ratio is calculated by dividing the investment in the annuity (the amount paid in) by the expected total return (the total amount expected to be received from the annuity). The result is the percentage of each payment that is considered a return of the investment and is thus not taxable. The remainder of the payment is taxable as ordinary income.