Presumptive taxation for foreign construction companies: deemed income on project receipts, lower showing permitted with audited books. A special presumptive rule for foreign companies in civil construction and power project erection computes taxable profits as a fixed percentage of receipts; taxpayers may show lower income only if they maintain books and obtain an audit, triggering scrutiny, and where profits are declared under the provision no set off of unabsorbed depreciation or brought forward losses is allowed, though specified other deductions remain available.