Charge of income-tax on total previous-year income, subject to Act provisions, with withholding or advance payment mechanisms. Charge of income-tax is founded on Section 4, which provides that income-tax shall be charged on the total income of the previous year at rates enacted by Parliament and subject to the provisions of this Act; where tax is to be charged for a period other than the previous year, it shall be charged accordingly. For income so chargeable, tax is to be deducted at source or paid in advance where such mechanisms apply under the Act, thereby coupling the substantive basis of charge with statutory collection procedures.