(a) Service charges shall not apply when credit is extended and payments are made within the standard credit period. The term standard credit period, as used in the preceding sentence, means:

1. (1) the credit period prescribed in section 830.1 of this Part; or
2. (2) a substitute credit period published in a tariff rule pursuant to the authorization in section 830.5 of this Part.

(c) Carriers may, by tariff rule, establish service charges for payments made after the expiration of an authorized credit period. Such a rule shall:

1. (1) institute such charges on the day following the last day of an authorized credit period; and

2. (2) notify shippers:

   1. (i) that its only purpose is to prevent a shipper who does not pay on time from having free use of funds due to the carrier;
   2. (ii) that it does not sanction payment delays; and
   3. (iii) that failure to pay within the authorized credit period will, despite this provision for such charges, continue to require the carrier, before again extending credit, to determine in good faith whether the shipper will comply with the credit regulations in the future.