(f)where regular books of account are not maintained by the assessee, the return is accompanied by a statement indicating the amounts of turnover or, as the case may be, gross receipts, gross profit, expenses and net profit of the business or profession and the basis on which such amounts have been computed, and also disclosing the amounts of total sundry debtors, sundry creditors, stock-in-trade and cash balance as at the end of the previous year: