Board direction of income-tax authorities can reassign powers and specify jurisdiction, altering who handles assessments and returns. Section 120 authorises the Board to issue directions reallocating exercise of powers and functions among income-tax authorities, including authorising authorities to issue orders for subordinate officers. The Board may base directions on territorial area, persons, incomes or cases, empower senior officers to perform functions of others or designate alternate officers to exercise Assessing Officer powers, permit concurrent jurisdiction among Assessing Officers with hierarchy rules, and notify in the Official Gazette the authority responsible for receipt of returns or other acts for specified persons or classes.