Presumptive taxation for foreign construction companies in turnkey power projects: deemed business income unless audited books are maintained. A presumptive taxation regime applies to foreign companies engaged in civil construction or erection and testing of power plants in certain turnkey power projects, treating receipts for such work as deemed business income. Assessees may declare lower profits if they maintain books and secure audit under section 44AB, triggering scrutiny under section 143(3). Chapter VI-A deductions are available, but set off of unabsorbed depreciation and brought forward losses is disallowed for years where profits are declared under this provision; current year losses may be set off subject to these restrictions.