This document explains the Maximum Marginal Rate (MMR) of Income Tax, which is the highest tax rate applied to income, including surcharges and cess. It details the specific rates applicable for AY 2021-22 for individuals, AOPs, and BOIs, as well as special rates for trusts. The document also outlines various scenarios where the MMR applies, such as income from trusts, investment funds, and business trusts. This guide is useful for taxpayers seeking to understand their highest potential income tax liability.