(a) The account numbering plan used in this part consists of a system of three-digit whole numbers as follows:

(1) 100-199, Assets and other debits.

(2) 200-299, Liabilities and other credits.

(3) 300-399, Property accounts.

(4) 400-432 and 434-435, Income accounts.

(5) 433, 436 and 439, Retained earnings accounts.

(6) 457-458, Revenue accounts.

(7) 500-599, Electric operating expenses.

(8) 800-894, Gas operating expenses.

(9) 900-949, Customer accounts, customer service and informational, sales, and general and administrative expenses.

(b) The numbers prefixed to account titles are to be considered as parts of the titles. Each service company, however, may adopt for its own purposes a different system of account numbers (See also General Instructions in §367.3(d)) provided that the numbers prescribed in this part must appear in the descriptive headings of the ledger accounts and in the various sources of original entry; however, if a service company uses a different system of account numbers and it is not practicable to show the prescribed account numbers in the various sources of original entry, the reference to the prescribed account numbers may be omitted from the various sources of original entry. Each service company using different account numbers for its own purposes must keep readily available a list of the account numbers that it uses and a reconciliation of those account numbers with the account numbers provided in this part. It is intended that the service company's records must be kept so as to permit ready analysis by prescribed accounts (by direct reference to sources of original entry to the extent practicable) and to permit preparation of financial and operating statements directly from the records at the end of each accounting period according to the prescribed accounts.