A computerized method of administering an annuity product having a withdrawal feature and a guarantee comprises the steps of establishing an annuity account from which withdrawals can be made, inputting data relating to the annuity account, paying withdrawals to the account owner, and providing a guarantee. Inputted data relating to the account includes a maximum withdrawal rate for a given withdrawal frequency. The guarantee provides that, even if the account value is exhausted before the end of a specified time period, amounts up to the maximum withdrawal will continue to be paid for the specified period, provided that withdrawals before the account value is exhausted do not exceed the maximum rate. The specified time period may be a lifetime period, a period of years or months chosen by the account owner when the account is established, or a period during which withdrawals at least equal a specified percentage of the account value, or a highest account value achieved, as of a specified date. The method may further include the step of establishing a charge to pay for the guarantee.