Section 1220.030 - Maintenance of records(a) Each lessee subject to this part 1220 shall establish and maintain such records as are necessary to determine for each NPSL:(1) The volume and disposition of all oil and gas production saved, removed or sold for each month;(2) The value of all oil and gas production saved, removed or sold for each month;(3) The amount and description of costs and credits to the NPSL capital account;(4) The amount and description of all costs of acquisition, construction, and operation of equipment and facilities furnished by the lessee and charged to the NPSL capital account under § 1220.011(g) . Such records shall include worksheets or other documents that indicate the method used to calculate the amount of each charge made under § 1220.011(g) ;(5) The cumulative balance of costs and credits to the NPSL capital account; and(6) The inventory of materiel.(b) The ledger cards showing the charges and credits to the NPSL capital account shall be maintained until thirty-six months after the cessation of NPSL operations by the lessee. All other documents, journals and records shall be maintained for thirty-six months from the due date or date of mailing of the statement of account on an NPSL, whichever comes later, except that nothing in these regulations shall limit the time of investigation or the need to produce records when prima facie evidence of fraud or willful misconduct is obtained with respect to the government's interest in the NPSL.45 FR 36800, May 30, 1980, as amended at 75 FR 61087 , Oct. 4, 2010