(a) For purposes of this section, the cost base for the allowance for capital recovery in a particular month shall consist of the sum of:

(1) All allowable direct and allocable joint costs chargeable to the NPSL capital account during the month less any costs specified in § 1220.012(c); plus

(2) The value of contract services chargeable to the NPSL capital account during the month pursuant to § 1220.011(e); plus

(3) The capital recovery period overhead allowance, calculated in accordance with § 1220.012(a), that is chargeable to the NPSL capital account for the month; less

(4) Production revenues and other credits received during the month.

(b) If the cost base for a month is greater than zero (that is, if the sum of the charges specified in paragraphs (a) (1) through (3) of this section exceeds the value of production revenues and other credits), the allowance for capital recovery shall be calculated by multiplying the cost base by the capital recovery factor, and shall be debited to the NPSL capital account as specified in § 1220.021(b).

(c) If the cost base for a month is less than zero, the allowance for capital recovery for the NPSL capital account shall be calculated by multiplying the resulting negative cost base by the capital recovery factor. The negative product of this calculation shall be debited to the NPSL capital account as specified in § 1220.021(b).

(d) No allowance for capital recovery shall be calculated on the charges or credits related to any time period after the end of the capital recovery period.