(a) Interest will accrue on all debts from the date when the first notice of the debt and the interest requirement is mailed to the last known address or hand-delivered to the debtor if the debt is not paid within 30 days from the date the first notice was mailed. The MSPB will charge an annual rate of interest that is equal to the average investment rate for the Treasury tax and loan accounts on September 30 of each year, rounded to the nearest whole per centum. This rate, which represents the current value of funds to the United States Treasury, may be revised quarterly by the Secretary of the Treasury and is published by the Secretary of the Treasury annually or quarterly in the Federal Register and the Treasury Financial Manual Bulletins.

(b) The rate of interest initially assessed will remain fixed for the duration of the indebtedness, except that if a debtor defaults on a repayment agreement interest may be set at the Treasury rate in effect on the date a new agreement is executed.

(c) The MSPB shall charge debtors for administrative costs incurred in handling overdue debts.

(d) Interest will not be charged on administrative costs.

(e) The MSPB shall assess a penalty charge, not to exceed 6 percent per year on debts which have been delinquent for more than 90 days. This change shall accrue from the date that the debt became delinquent.

(f) The Chairman or his designee may waive in whole or in part the collection of interest and administrative and penalty charges if determined that collection would be against equity or not in the best interests of the United States. The MSPB shall waive the collection of interest on the debt or any part of the debt which is paid within 30 days after the date on which interest began to accrue.