The STT Trap on Options Expiry Day and How to Avoid It
Letting a slightly in the money option expire instead of selling it can wipe out the whole profit, because Securities Transaction Tax on an exercised option is charged on the settlement value of the contract, not on the small premium. The STT trap is the jump in tax you pay when an in the money option is exercised at expiry, since the 0.15% rate applies to settlement value rather than to premium.
Squaring off minutes earlier can cost a few rupees in STT. Letting it expire can cost a few thousand.
What follows: the rate card, the arithmetic on one Nifty lot, why exercise is treated differently from a sale, and a routine to run every expiry day.
STT rates effective 1 April 2026
| Segment | Rate | Charged on |
|---|---|---|
| Equity delivery | 0.1% on both buy and sell | Turnover |
| Equity intraday | 0.025% on the sell side | Turnover |
| Futures | 0.05% on the sell side | Contract value |
| Options, sale of an option | 0.15% on the sell side | Premium |
| Options, exercised or assigned | 0.15% | Settlement value, paid by the buyer |
Read the last two rows together and the problem is visible. Same 0.15% rate, completely different base. Premium is a small number; settlement value of the contract is a large one.
Why exercise is treated differently from a sale
Sell an option in the market and you transfer a contract to another trader, so the taxable amount is the premium that changed hands.
When an in the money option is exercised at expiry, what gets taxed is the settlement of the contract itself. The base moves from premium to settlement value, and the option buyer pays it.
Two facts make this an expiry day issue. Index and stock options on NSE are European style, so they can only be exercised at expiry. And index options are cash settled while stock F&O contracts are physically settled, a larger problem for single stock positions. Our explainer on how options expiration works covers that session.
Worked example: one Nifty lot, two very different outcomes
Suppose the Nifty lot size is 75. Lot sizes are revised periodically, so confirm the current figure and expiry schedule on the exchange website.
You bought one lot of a Nifty 25,000 call at a premium of Rs 8.
- Cost: 8 x 75 = Rs 600
- Nifty final settlement value on expiry: 25,040
- Intrinsic value: 25,040 minus 25,000 = 40 points, so 40 x 75 = Rs 3,000
- Gross profit before charges: 3,000 minus 600 = Rs 2,400
A four fold gain. Now compare the two exits.
Route one: square off at Rs 40 before the close. STT is 0.15% on the premium. Premium value is 40 x 75 = Rs 3,000, so STT = 0.15% x 3,000 = Rs 4.50. Add brokerage, exchange charges, GST, stamp duty and SEBI fees and your total cost is still modest.
Route two: do nothing and let it expire in the money. The option is exercised and STT is charged at 0.15% on the settlement value. Settlement value = 25,040 x 75 = Rs 18,78,000, so STT = 0.15% x 18,78,000 = Rs 2,817.
Your Rs 2,400 profit becomes a loss of about Rs 417 before any other charge. Two bills for the same position, differing by a factor of more than 600.
That is the trap in one calculation. The rate never changed, only the base.
The rule of thumb that follows
The thinner the intrinsic value relative to the strike, the worse the ratio. A deep in the money option with several hundred points of intrinsic value can absorb the exercise STT and still leave a profit. An option 10 or 20 points in the money cannot.
Check how your broker computes exercise STT. One old contract note from an expiry you held to settlement shows exactly how yours was calculated.
How do you avoid the STT trap?
- Set a reminder for every expiry you hold a position into. Most people are not careless, just busy at 3 PM.
- Around 2:30 PM, list every leg you hold and mark each as in the money or out of the money against spot.
- Square off every in the money long option. Even a scratch exit at a rupee or two of slippage beats an exercise bill in the thousands.
- Do not wait for the last five minutes. Bids thin out near the close, and a leg you meant to sell at Rs 40 may only find a buyer at Rs 25.
- Close whole spreads. Leaving one in the money leg to settle while exiting the other turns a hedged position into an unhedged tax event.
- Exit single stock options well before expiry, since those are physically settled and bring a delivery obligation plus higher margins in the final days.
- Ask your broker whether any close to the money instruction exists in your account. Never assume one does.
Out of the money options need no action. They expire worthless, nothing is exercised, and your loss is the premium you already paid. If that distinction is fuzzy, our guide on ITM versus OTM options helps.
What about option sellers?
If you sold the option, your STT was already charged at 0.15% on the premium received. The exercise STT is paid by the buyer.
Your risk is different: assignment. A short option finishing in the money is settled against you, and for stock options that means a real delivery obligation in shares, covered in our piece on assignment risk in options.
Risk note: expiry day concentrates volatility, spreads widen and premiums move violently. Options can lose their entire value, so size legs so a total loss is survivable.
How this shows up in your tax return
STT is a transaction cost, not income tax. It is deducted at the trade and appears line by line on your contract note.
Separately, F&O income is non speculative business income reported in ITR-3, where it can be set off against other business income. Intraday equity is speculative business income. Losses carry forward 8 years, or 4 for speculative losses, but only if you file by the due date.
Because STT is a business expense there, a large exercise hit does reduce taxable business income. That softens the blow without undoing it.
Frequently Asked Questions
Does the STT trap apply to Bank Nifty and other index options too?
Yes. The exercise treatment applies to any in the money option that goes to settlement, so Nifty, Bank Nifty and other index options are affected. A larger index level means a larger settlement value and a bigger exercise bill for the same lot. Confirm current lot sizes and expiry days on the exchange website.
Will my broker automatically square off my in the money options on expiry day?
Do not count on it. Some brokers run risk based square off in specific cases, particularly stock options heading into physical settlement, and some send warnings. Policies differ and change. Assume the position is yours to close and treat any automatic action as a bonus, not a backstop.
What happens if my in the money option has no buyers late on expiry day?
You are choosing between a poor exit price and settlement. Compare them in rupees: slippage of 15 points on a 75 unit lot is Rs 1,125, still cheaper than exercise STT on a barely in the money contract. The real fix is exiting earlier while the book is deep.
Can I claim STT back or set it off against my tax liability?
You cannot claim a refund of STT. In the F&O context, where income is non speculative business income, STT is allowable as a business expense and reduces taxable profit. That is a partial offset at your rate, not a recovery. Keep contract notes and the annual charge statement for filing.
Why do experienced traders still get caught by this?
Usually a forgotten cheap leg in a multi leg structure, or a strike comfortably out of the money at 2 PM that drifted in the money by 3:25 PM. Both are process failures, not knowledge gaps. Our list of common options trading mistakes covers similar errors.
Key Takeaways
- Selling an option costs 0.15% STT on the premium. Letting it be exercised costs 0.15% on settlement value, a far larger base.
- In the example, a Nifty 25,000 call bought at Rs 8 and settling at 25,040 cost Rs 4.50 in STT if squared off and about Rs 2,817 if exercised, turning a Rs 2,400 profit into a loss.
- Barely in the money options are the dangerous ones. Deep contracts hold enough intrinsic value to absorb the exercise charge.
- Square off in the money longs by mid afternoon, not in the closing minutes when bids disappear.
- Single stock options are physically settled, so exit well before expiry to avoid a delivery obligation on top of the tax.
- STT is a business expense against F&O income in ITR-3, which softens the hit but never recovers it.
