Of the nearly 5.8 crore assessees who filed returns for the last fiscal, 55.4 lakh had claimed housing rent allowance (HRA), which is roughly 9.5% of the base. Within this, around 43 lakh had annual HRA of under Rs 1 lakh. Hence, Centre expects up to 80% of tax assessees to move to the new flat-rate regime, given that not many use HRA benefits for investments.

from Times of India https://timesofindia.indiatimes.com/business/india-business/80-may-switch-tax-regimes-government/articleshow/73946716.cms