(a) When rate adjustment filings that involve a rate increase are filed more than 12 months apart, any interim rate adjustment authority must first be added to the schedule of banked rate authority before the unused rate adjustment authority is calculated.

(b) Interim rate adjustment authority for a class is equal to the Base Average applicable to the second rate adjustment filing (as developed pursuant to § 3030.142) divided by the Recent Average utilized in the first rate adjustment filing (as developed pursuant to § 3030.142) and subtracting 1 from the quotient. The result is expressed as a percentage and immediately added to the schedule of banked rate authority as of the date the rate adjustment filing is filed. If the Commission announces that rate authority calculated pursuant to subpart D of this part or § 3030.222 are available and no rate adjustment is filed before the Commission subsequently announces that further rate authority calculated pursuant to subpart D of this part or § 3030.222 are available, then the amount of rate authority calculated pursuant to subpart D of this part and § 3030.222 in the first Commission announcement shall be added to the interim rate adjustment authority.

(c) Unused rate adjustment authority for a class is equal to the difference between the maximum rate adjustment authority as summarized by § 3030.127 and calculated pursuant to subparts C through G of this part and this subpart, as appropriate, and the percentage change in rates for the class calculated pursuant to § 3030.128, subject to the limitations described in paragraph (d) of this section.

(d) For rate adjustment filings that involve a rate increase, unused rate adjustment authority cannot exceed the unused portion of rate authority calculated pursuant to subparts C and D of this part and § 3030.222.