Assessment powers: Assessing Officer may compel production of accounts and determine chargeable expenditure and tax. The Assessing Officer may serve notices on persons who furnished returns or were notified under section 8, requiring production of accounts, documents or other evidence and may issue further notices for additional material. After considering the produced records and any relevant gathered material, the officer must make a written assessment of chargeable expenditure and determine the amount of tax payable based on that assessment.