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Securities Transaction Tax is a small, automatic tax on every options transaction in India — and the subject of a lot of outdated "STT trap" advice still circulating online, describing rules that changed years ago. This page covers the actual current rules, and where the old trap reputation came from.

Note on currency of this page: STT rates are set by government notification and are revised periodically — most recently on 1 April 2026 under Budget 2026. The figures below reflect that current rate, but always confirm the live rate with your broker or the exchange before relying on it for a real trade.

Securities Transaction Tax (STT) is collected automatically by the exchange on securities transactions, including F&O trades. For options specifically, STT applies in two different situations, calculated two different ways:

• Selling an option — STT is charged on the option's premium value. There is no STT on buying an option.
• Letting an option get exercised at expiry — STT is charged on the option's intrinsic value (the difference between the settlement price and the strike), not the premium or the full contract value.

As of the current rate, both situations are taxed at the same percentage — 0.15% — but on genuinely different bases, which is the key detail the rest of this page works through.

Before September 2019, STT on an exercised option was calculated on the full settlement value of the contract (essentially the settlement price multiplied by the lot size), not just the profit portion. This created a real, severe trap: a narrowly profitable ITM position could face an STT bill far larger than the actual profit, sometimes turning a winning trade into a net loss purely from tax.

Since September 2019, the calculation basis changed to intrinsic value only — the actual profit portion, not the full contract value. This single change reduced typical exercise-STT bills by roughly 98–99% in the scenarios that used to cause the trap. A great deal of "STT trap" content still online describes the pre-2019 rules as if they're current — worth knowing before taking that advice at face value.

Suppose you're long 1 lot (65) of a Nifty 24,000 call, and Nifty settles at 24,100 at expiry — 100 points in-the-money.

Under the current rules (intrinsic-value basis):

1. Intrinsic value: (24,100 − 24,000) × 65 = ₹6,500 — this is also your profit.
2. STT on exercise: 0.15% × ₹6,500 = ₹9.75.
3. That's a tiny fraction of the ₹6,500 profit — nothing close to a "trap" at this rate and basis.

Under the old, pre-September-2019 rules (full settlement value basis, at that era's lower 0.125% rate), the same position would have faced:

1. Full settlement value: 24,100 × 65 = ₹1,566,500.
2. Old STT: 0.125% × ₹1,566,500 = ₹1,958.13.
3. That's 30.1% of the entire ₹6,500 profit, gone to tax on a single narrowly-ITM position — this is the scenario that earned "STT trap" its name.

A related, still-common piece of advice is "always sell your ITM options before expiry, never let them exercise." Under the current intrinsic-value-basis rules, this needs a second look. Continuing the same example — selling that call in the market moments before expiry, at a premium of roughly 105 (the 100-point intrinsic value plus a few points of residual extrinsic value):

In this example, exercising is actually slightly cheaper in STT than selling — because the premium (which includes a bit of residual extrinsic value) is always at least as large as the intrinsic value alone. This is the mirror image of the old advice: under current rules, the STT comparison alone no longer clearly favors selling. There are still good reasons to square off before expiry (covered below) — STT just isn't the main one anymore.

• Stock options carry physical delivery. Unlike index options (cash-settled), an ITM stock option that's exercised creates an actual delivery obligation — you either receive or deliver shares, with all the funding and follow-on brokerage that involves.
• Certainty of price. Selling locks in the exact market price at that moment. Waiting for expiry settlement means relying on the exchange's own settlement price calculation, which may differ slightly from what you could have captured by selling.
• Capturing any remaining extrinsic value. Right up to the very last moments before expiry, an option may still carry a small amount of extrinsic value — letting it expire rather than selling forfeits that residual value, an opportunity cost separate from STT entirely.

• Every strategy on this site involves at least one sell leg (or, for defined-risk long strategies, potentially letting a leg expire ITM) — STT is a small but real cost layered on top of the strategy's own max profit and max loss figures shown throughout this site.
• High-frequency, small-margin strategies feel STT more — a trader running many trades a month accumulates the per-trade STT cost in a way a single, larger position doesn't notice as much.
• Multi-leg strategies with several sell legs (like an Iron Condor or Short Strangle) accumulate STT across every leg sold, worth factoring into the real breakeven alongside the option premiums themselves.

• STT rates change by government notification and have changed more than once in recent years — always verify the current rate with your broker or the exchange rather than assuming a figure stays fixed indefinitely.
• A great deal of older "STT trap" content online describes pre-2019 rules — the underlying mechanics changed substantially since then, as covered above.
• STT is only one of several transaction costs — brokerage, exchange transaction charges, GST, and stamp duty also apply and aren't covered on this page.