The CU*BASE system does not have an automated method of calculating the payoffs for loans with a 30/360 interest calcuation type.  The number of variables relative to the timing of the payoff, interest accrual, and interest calculation methods require that this function be done manually by someone who thouroghly understands the mortgage market.
 
Interim payoffs on 30/360 loans are typically calculated by using the daily interest calculation method.   As an example, the member calls on the 5th, has already made their payment for the month, and would like to know what the payoff is for the 28th.  In this case the proper formula would be:  Principal * Interest rate/365 * the number of days from the first of the month to the payoff day + any accrued interest + principal.  Industry standards dictate not including the day of payoff in the interest calculation.  Remember on the 20th the system will calculate a full 30 days of accrued interest.  If the member pays the loan off on the 28th the number of days between the 28th and the end of the month will need to be credited to the interest due prior to applying the payoff.  Another example would be if the member calls on the 5th, has made their payment for the month, and would like a payoff on the loan for the 10th of next month.  In this case the proper formula to use would be:  Principal * Interest rate/12 (for the current month) + Principal * Interest rate/365 * the number of days between the first and the payoff date but not including the day the loan is paid off + outstanding interest + principal.  Again, remember when the member pays off the loan that interest has not accrued for the 19 days in the month and must be added to the interest due field prior to applying the payoff.