Tax exemption for welfare board income under section 10(46) subject to non-commercial activity and return-filing conditions. Tax exemption is notified under section 10(46) for the Chandigarh Building and Other Construction Workers Welfare Board in respect of specified income comprising cess collection, beneficiary contributions, and interest earned on bank deposits. The exemption is subject to conditions that the Board must not engage in commercial activity, its activities and specified income must remain unchanged, and it must file returns under section 139(4C)(g); non-compliance may attract penal action and withdrawal of the exemption. The notification applies retrospectively for certain assessment years and prospectively for later assessment years.