What is the IGFA Act's architecture?

The Income Tax Act 2058 (2002) — the direct-tax core: the tax's heads (the income-from- business (the business-and-investment income), the employment (the salary-and-benefits), the investment (the interest-dividend-rent-gain faces)); the taxpayer's classes (the resident-and-non- resident (the source rules)); the assessment's machinery (the self-assessment + the IRD's audit- and-reassessment); the deductions-and-exemptions (the expenses' deductibility; the exempt- income faces (the cooperative-and-social sector's lines)); the rates (the Finance Act's annual variation — the slabs-and-corporation rate's budget-night changes); the relevance: the revenue's biggest single source (the modern system's anchor — the 2058 Act's consolidation of the scattered old laws).