Exemption under section 35AC approves eligible projects and institutions for tax relief over specified assessment years. Exemption under section 35AC approves named charitable and development institutions as sponsors of specified eligible projects and prescribes the maximum approved estimated cost for each project; institutions must undertake the approved projects within the scope and cost limits set in the notification table to qualify for the income-tax exemption, and the notification fixes the period of effectiveness for approvals in relation to particular assessment years, with subsequent substitutions amending project descriptions, cost ceilings and expiry schedules.