of section 167 or 168 of the Internal Revenue Code of 1986 if the taxpayer, in computing its cost of service for ratemaking purposes and reflecting operating results in its regulated books of account, reduces the excess tax reserve more rapidly or to a greater extent than such reserve would be reduced under the average rate assumption method. (2) Alternative Method for Certain Taxpayers If, as of the first day of the taxable year that includes the date of enactment of this Act— (A) the taxpayer was required by a regulatory agency to compute depreciation for public utility property on the basis of an average life or composite rate method, and (B) the taxpayer’s books and underlying records did not contain the vintage account data necessary to apply the average rate assumption method, the taxpayer will be treated as using a normalization method of accounting if, with respect to such jurisdiction, the taxpayer uses the alternative method for public utility property that is subject to the regulatory authority of that jurisdiction. (3) Definitions For purposes of this subsection— (A) Excess tax reserve The term excess tax reserve means the excess of— (i) the reserve for deferred taxes (as described in section 168(i)(9)(A)(ii) of the Internal Revenue Code of 1986 as in effect on the day before the date of the enactment of this Act), over (ii) the amount which would be the balance in such reserve if the amount of such reserve were determined by assuming that the corporate rate reductions provided in this Act were in effect for all prior periods. (B) Average rate assumption method The average rate assumption method is the method under which the excess in the reserve for deferred taxes is reduced over the remaining lives of the property as used in its regulated books of account which gave rise to the reserve for deferred taxes. Under such method, if timing differences for the property reverse, the amount of the adjustment to the reserve for the deferred taxes is calculated by multiplying— (i) the ratio of the aggregate