Presumptive taxation: eligible businesses deemed to earn a prescribed proportion of turnover for computing taxable business income. Presumptive taxation requires an eligible assessee engaged in an eligible business to have profits deemed as a prescribed proportion of total turnover or gross receipts, with standard business deductions treated as already allowed and no further deduction permitted; written down value is computed as if depreciation had been claimed; specified professions and certain income types are excluded; eligibility is conditioned on residence, entity type, turnover thresholds and mode of receipts, and departure from the scheme or excess total income triggers record keeping and audit obligations.