(a) A separate subdivision shall be maintained in account 141, Unamortized Debt Discount and Expense, for the excess of discount and debt expense over any premium related to each class of long term debt issued or assumed. (See pars. [12], [14] and [34] of subd. [a] of § 196.1.)

(b) Corresponding subdivisions shall be maintained in account 271, Unamortized Premium on Debt, for the excess of the premium over any discount and debt expense related to each class of long term debt issued or assumed.

(c) Each month there shall be credited to each subdivision of account 141, Unamortized Debt Discount and Expense, the amount applicable to such month under a plan the application of which will equitably distribute the balance therein over the life of the security. Amounts thus credited shall be concurrently charged to account 453, Amortization of Debt Discount and Expense.

(d) Correspondingly, each month there shall be charged to each subdivision of account 271, Unamortized Premium on Debt, the portion of such credit balance which is applicable to that month. Amounts thus charged shall be concurrently credited to account 454, Release of Premium on Debt—Cr.

(e) The utility may extinguish at any time through Surplus all or any part of the balance remaining in any subdivision of account 141, Unamortized Debt Discount and Expense, or account 271, Unamortized Premium on Debt.

(f) Except as provided in subdivision (c), (d) and (e) of this section, the balance in each of these accounts or subdivisions thereof shall be carried until the reacquisition of the securities to which it relates. At that time (unless otherwise ordered by the commission) a portion of the balance in the account or subdivision for the particular class of long term debt reacquired shall be transferred to account 502, Miscellaneous Credits to Surplus or account 514, Miscellaneous Debits to Surplus, as may be appropriate. Such portion shall be based on the relation of the amount of the particular issue of long term debt reacquired to the total outstanding before its reacquisition. This provision shall not apply to securities held alive in sinking or other funds.

(g) Except as provided in paragraph (10) of subdivision (e) of section 197.21, no discount or expense on long term debt shall be included in any account as a part of the cost of acquiring any property or as a part of the cost of operation.