Charge of income tax: taxed on total income with collection via TDS, TCS or advance tax under statutory rules. Section 4 sets the basis of charge: income tax is charged for each tax year at rates enacted by the Central Act on the total income of every person, and includes additional levies such as surcharge or cess. The Act allows charging tax for periods other than the tax year where specified, and requires payment by deduction at source, collection at source, or advance tax. Definitions of tax year, previous year, assessment year, person and assessee determine applicability, while the law as on the first day of the assessment year governs computation of total income.