A separate tenants ledger to record all transactions with tenants shall be maintained for each income analysis ledger (see § 1642-3.8). A tenants ledger sheet or card shall be prepared for each dwelling unit or commercial space, even though the space may be vacant. Tenants ledger sheets for units in buildings which have been demolished may be segregated in an inactive section of the respective tenants ledger. A specimen form of tenants ledger sheet designed for use in a hand-posted ledger is shown as Exhibit 20 of Appendix S-8. The specimen form is a loose-leaf sheet, but cards may be used or forms designed for a visible filing system. Where machine-posting is employed, the form must, of course, be adapted to the requirements of the particular machine. Regardless of form, the tenants ledger sheet shall show the name of the local agency, the project number, the name and address of the tenant, the account number, the apartment size, the basic rent, surcharges (if any) and current authorized rent, the effective date of tenancy, the move-out and charge-through dates, the date and explanation of each charge and credit and the balance of the tenant's account. The local agency may add such other information as it deems desirable. Each dwelling unit and commercial space shall be assigned, in advance of initial occupancy, a number which shall reflect the building or stair-hall number and the apartment or commercial space number and which shall be recorded on the tenants ledger sheet as the account number. The tenants ledger sheets shall be arranged in a logical sequence by buildings, stair-halls, and apartment numbers. The sequence, once established, shall remain constant. The account numbers, once established, shall also remain constant notwithstanding that several tenants may have successively occupied the same unit. As a unit or space is leased, a new ledger sheet or card is prepared for the new tenant, the unit being identified by the account number assigned as above. The tenants ledger is controlled by the tenants charge and credit book (see Subpart 1642-4) and the total of the balances in the tenants ledger shall at all times agree with the control. A trial balance of the tenants ledger shall be taken at the end of each calendar month and preserved and dated to establish a formal and periodic proof of such agreement. The operation of the tenants ledger, the details of posting, etc., are described in Subpart 1642-4.