In the case of subdivision time sales where no interest is charged, the directions of Chapters XXI and XXIII give also the manner of auditing. If the special ledger (Form 15, Section 23) is used, the balances shown can easily be verified by adding machine lists. It may be well to urge the wisdom in all cases of calculating the unearned, i.e., the "reserve" profits; of keeping them in the balance sheet, and carrying to Profit and Loss only such surplus as the Gain account may contain in excess thereof (Section171).