One other change in withdrawal policy affects the “substantially equal” monthly payments option. Currently, investors may choose one of three types of such withdrawals, based on a dollar amount per month, a number of months to draw down the account balance, or life expectancy-based payments calculated according to actuarial tables. After the changeover, the TSP will no longer allow withdrawals based on a number of months. However, unlike the current policy, dollar amount based withdrawals will be changeable, as often as once a year. Also, there will be a one-time opportunity for someone taking a life expectancy-based monthly withdrawal to change to a dollar amount-based withdrawal.