A system for data processing for an account of a financial product has a processor and a memory. The processor receives an account value and a charge applicable to the account based on a fraction of the value of the account; on a basis of a second period, shorter than a first period. Throughout the first period, the processor calculates a fractional charge based on the value of the account, and updates the account value by decrementing the account 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 account value on one day during the first period to a sum of the fractional charges for the first period, and increases the account value by the difference if the first period charge is less than the sum of the fractional charges.