The head of an executive, judicial, or legislative agency shall charge a minimum annual rate of interest on an outstanding debt on a United States Government claim owed by a person that is equal to the average investment rate for the Treasury tax and loan accounts for the 12-month period ending on September 30 of each year, rounded to the nearest whole percentage point. The Secretary of the Treasury shall publish the rate before November 1 of that year. The rate is effective on the first day of the next calendar quarter.

The Secretary may change the rate of interest for a calendar quarter if the average investment rate for the 12-month period ending at the close of the prior calendar quarter, rounded to the nearest whole percentage point, is more or less than the existing published rate by 2 percentage points.

on which notice is mailed after October 25, 1982, if notice was first mailed before October 25, 1982; or

notice of the amount due is first mailed to the debtor at the most current address of the debtor available to the head of the executive or 1 legislative agency, if notice is first mailed after October 24, 1982.

is the rate in effect on the date from which interest begins to accrue under subsection (b) of this section; and

remains fixed at that rate for the duration of the indebtedness.

a charge to cover the cost of processing and handling a delinquent claim; and

a penalty charge of not more than 6 percent a year for failure to pay a part of a debt more than 90 days past due.

if a statute, regulation required by statute, loan agreement, or contract prohibits charging interest or assessing charges or explicitly fixes the interest or charges; and

to a claim under a contract executed before October 25, 1982, that is in effect on October 25, 1982.

The head of an executive, judicial, or legislative agency may increase an administrative claim by the cost of living adjustment in lieu of charging interest and penalties under this section. Adjustments under this subsection will be computed annually.