The Montague-Chelmsford Report formed the basis of:

The Montagu‑Chelmsford Report (1918) provided the framework for the constitutional changes that were enacted by the British Parliament as the Government of India Act, 1919. Contemporary accounts state that the Report’s recommendations — including introduction of dyarchy in the provinces, enlargement of legislative councils, and a bicameral central legislature — were embodied in the 1919 Act, making it the direct legislative outcome of the Montagu‑Chelmsford scheme [2]. Thus the Report formed the theoretical and practical basis for the Government of India Act of 1919 rather than earlier or later Acts like those of 1909, 1935 or 1947 [2].

Sources

1. [1] Introduction to the Constitution of India, D. D. Basu (26th ed.). > Chapter 1: THE HISTORICAL BACKGROUND > Utility of a Historical Retrospect. > p. 4
2. [2] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 26: Constitutional, Administrative and Judicial Developments > Government of India Act, 1919 > p. 509