Presumptive taxation for nonresident business receipts: fixed-percentage computation of taxable profits with limited rebuttal by audited accounts. Special rules prescribe computation of income on a presumptive basis for specified business activities carried on by specified non-resident taxpayers, excluding conflicting provisions. The statute lists business categories and prescribes a fixed percentage of defined receipts as taxable profits; an assessee in several categories may claim lower actual profits only by maintaining required books and obtaining an audit report. No loss, deduction or allowance is permitted against income computed under the presumptive formula, and written down value is computed as if depreciation had been claimed and allowed. Definitions and applicability conditions for certain categories are provided.