Think of it this way: you bought shares of Reliance Industries in January and sold them in September of the same year — that's a Short-Term Capital Gain (STCG). Most students assume it simply gets added to salary income and taxed at slab rates. Section 111A says: not if STT was paid on that transaction.
Two conditions must both be satisfied for Section 111A to kick in. First, the asset sold must be an equity share in a company, a unit of an equity-oriented fund (think equity mutual funds with 65%+ equity allocation), or a unit of a business trust — and it must have been held for 12 months or less to qualify as short-term. Second, the sale must happen on a recognised stock exchange with Securities Transaction Tax (STT) charged on it. Off-market transfers, private deals, and sales of delisted shares fail this second test and fall under normal slab taxation instead.
When both conditions are met, the gain is taxed at a flat rate of 20% — regardless of your income slab. (Important for May 2026: the Finance (No. 2) Act 2024 raised this rate from 15% to 20% for transfers on or after 23 July 2024. The bare Act still shows 15% — update your notes.) Three more rules the exam loves: (1) Chapter VIA deductions (80C, 80D, etc.) cannot be set off against Section 111A gains — they are allowed only against the balance income. (2) The rebate under Section 87A is computed on income excluding these special-rate gains. (3) There is a special basic exemption proviso for resident individuals and HUFs: if your income other than STCG is below ₹2,50,000 (basic exemption under old regime), you first fill up that unused exemption against the STCG, and tax only the remainder at 20%. This proviso is a high-frequency exam trap — students ignore it and lose marks. This section appears regularly as a 4–6 mark numerical in the Tax paper, either standalone or as part of a full income computation.