A system for administration of an insurance annuity account has a processor and a memory. The processor receives a net asset value of the account at a commencement of a first period and a charge applicable to the account based on a fraction of the net asset value of the account; on a basis of a second period, shorter than the first period, throughout the first period: the processor calculates a fractional charge based on the net asset value of the account, and updates the net asset value by decrementing the net asset value in the amount of the fractional charge. At the end of the first period, the processor compares a charge for the first period based on the net asset value of the account on one day during the first period to a sum of the fractional charges for the first period, and increases the net asset value by the difference if the first period charge is less than the sum of the fractional charges.