Maintenance of cost records required to enable per-unit costing, reconciliation, retention and managerial control under corporate rules. Companies covered must keep cost records for each financial year from 1 April 2011, enabling calculation of per unit costs, cost of sales and margins on periodic bases, maintained in accordance with accepted cost accounting principles and standards with any variations explained. Records must enable managerial control and be reconciled with audited financial statements, indicating excluded expenses or incomes and explaining variations, and retained in good order for at least eight financial years or for the company's existence if shorter.