Taxes on income: DTAA defines scope to include income taxes and similar future taxes with mutual notification. Article 2 limits the treaty to taxes on income, including taxes on total income and specific income elements such as gains from alienation of property and taxes on wages or salaries; it identifies the existing domestic income tax instruments in the Contracting States and extends coverage to identical or substantially similar taxes enacted later, while requiring mutual notification of significant tax-law changes by the competent authorities.