Wang, May Yee, Measuring the Scope of International Accounting Harmonisation and Standardisation – A Study of South East Asia, Doctor of Philosophy (Business with Management), June, 2023, University of Plymouth, England. Using South East Asia as the illustration of developing countries, this research assessed the degrees of harmonisation of selected accounting measurement practices. This research empirically investigates whether the efforts prepared by South East Asia since the early 1990s to harmonise their national standards with IAS have been practical. In this research, financial data from the ASEAN top 100 organisations’ financial statements for the year 2015 to 2016 have been collected, of which 27 from Malaysia, 21 from Singapore, 21 from Thailand, 16 from Indonesia, 14 from the Philippines and one from Vietnam. The I index that is established by Van der Tas (1988) has been applied to evaluate the extent of harmonisation. Meanwhile, the C indices have been applied to verify the equivalence of the proportions of accounting measurement choices in South East Asia. In general, the outcomes of this research reveal that the accounting transformation in South East Asia has been successful in harmonising national accounting standards with IAS. The results of the I index and the C indices indicate a comparatively higher level of harmonisation in the areas of foreign currency translation, accounting for pensions and retirements benefits costs and accounting for investments. In contrast, noticeable differences between national accounting standards and IAS still exist in some significant financial measurements. A comparatively lower level of harmonisation discovers in the areas of inventory valuation, depreciation of property, plant and equipment and goodwill amortisation. Lower degrees of harmonisation are because of non-compliance by organisations and the level of adjustability accessible in specific accounting treatments.