(a) An interest charge shall be assessed on unpaid and underpaid amounts from the date the amounts are due.

(b) The interest charge on late payments shall be at the underpayment rate established by the Internal Revenue Code, 26 U.S.C. 6621(a)(2) (Supp. 1987).

(c) Interest will be charged only on the amount of the payment not received. Interest will be charged only for the number of days the payment is late.

(d) A portion of the interest collected will be paid to a State where the State shares in mineral revenues from Federal leases.

(e) An overpayment on a lease or leases may be offset against an underpayment on a different lease or leases to determine a net underpayment on which interest is due pursuant to conditions specified in § 1218.42.