Tax option for resident cooperative societies: restricted deductions and irrevocable election govern alternative income computation. Resident co-operative societies may elect computation of total income under Section 115BAD at a concessional rate subject to prescribed conditions; the option, once exercised by the due date for the return, is irrevocable and applies to subsequent years but becomes invalid if conditions are not met. The computation excludes specified deductions and disallows set off or carry forward of losses or depreciation attributable to those excluded deductions; depreciation must be claimed under the principal depreciation provision as prescribed and prescribed adjustments to written down value apply for prior unrelieved block depreciation. A modified rule preserves a specified deduction for eligible IFSC Units subject to that section's conditions.