After all subsidiary ledgers have been balanced to the respective general ledger accounts, a pre- closing trial balance of the general ledger shall be taken to prove that the sum of the debit balances equals the sum of the credit balances. The subsidy to be taken into income shall then be computed in accordance with Part 1648 and an entry prepared and posted. The income and expense analysis ledgers may now be ruled off. It is recommended that a post-closing trial balance of the general ledger be prepared when the closing entries prescribed in section 1647-7.5, below, have been posted. Copies of all trial balances shall be preserved for use of the division's auditor. See Exhibit 1 of Appendix S-12 for form to be used for trial balance and reconciliation of funds.