Article 43 defines 'Taxable Income' as the residual amount of gross income after all allowable expenses have been deducted and all statutory set-offs or exemptions have been applied. This 'net' figure represents the final base upon which the income tax rate is actually imposed for any given tax year. By clearly distinguishing between gross and taxable income, the Law provides a structured path for businesses to calculate their liability while ensuring that only net profits (after necessary business costs) are subject to taxation.