Presumptive taxation under section 44AD fixes business income by applying turnover-based rates, with reduced rates for electronic receipts. Taxable business income under the presumptive taxation scheme is computed on a presumptive basis as a prescribed percentage of total turnover or gross receipts, with a reduced percentage where receipts are realized by account payee cheque, draft, electronic clearing system or other prescribed electronic modes; actual income may be declared higher than the presumptive amount.