The one rule to remember

Effective 01 September 2025, NSE and BSE consolidated their expiry days:

💡 The memory rule

NSE → Tuesday. BSE → Thursday.

Every NSE product (Nifty 50, Bank Nifty, Finnifty, Midcap Nifty, Nifty Next 50, and all single-stock options) now expires on Tuesday — weekly if it has weeklies, else last Tuesday of the month.

Every BSE product (Sensex, Bankex, Sensex 50) now expires on Thursday — weekly for Sensex, monthly for the rest.

The full Indian expiry calendar (post 01-Sep-2025)

Specifications verified: 17 September 2026

Specifications change — always verify current lot sizes, expiry days, and margins with your broker before trading.

Instrument	Exchange	Weekly	Monthly (last)	Settlement
Sensex (most-traded)	BSE	Thursday	Thursday	Cash
Nifty 50	NSE	Tuesday	Tuesday	Cash
Bank Nifty	NSE	—	Tuesday	Cash
Finnifty	NSE	—	Tuesday	Cash
Midcap Nifty	NSE	—	Tuesday	Cash
Nifty Next 50	NSE	—	Tuesday	Cash
Sensex 50	BSE	—	Thursday	Cash
Bankex	BSE	—	Thursday	Cash
Stock options (Reliance, TCS, HDFC…)	NSE	—	Tuesday	Physical delivery

Only two products carry weekly options now: Sensex (BSE Thursday) and Nifty (NSE Tuesday). All other weeklies were discontinued in SEBI’s 2024 F&O consolidation.

What changed on 01 September 2025

Before the switch:

Nifty weekly expired Thursday
Sensex weekly expired Tuesday

After the switch:

Nifty weekly moved to Tuesday
Sensex weekly moved to Thursday
They swapped days. Every NSE product also went from last Thursday of month to last Tuesday.

For traders, this means:

Any article or reference dated before Sep 2025 shows OLD expiry days — always verify
Your muscle memory around expiry-day routines needed to shift
Sensex is now the “Thursday product”; Nifty is now the “Tuesday product”

How option value decays across the cycle

Time decay — option value from 45 DTE → expiry (K = ₹25,000)

At 30d

Call: ₹503.2

Put: ₹359.7

Notice the acceleration in the last week: ATM options bleed slowly at 45 DTE, then dump rapidly in the final 5 days. This is why premium sellers love the last week of an expiry cycle — and why buyers should avoid it.

Picking the right expiry for your strategy

For selling premium (short strangles, iron condors)

Weekly cycle — enter early, exit 1-2 days before expiry:

Sensex weekly: enter Friday afternoon (day after Thursday expiry clears), exit following Wednesday
Nifty weekly: enter Wednesday afternoon (day after Tuesday expiry clears), exit following Monday

Avoid entering less than 2 days from expiry (gamma risk) or holding into the last hour (pin risk).

For buying volatility (long straddles, backspreads)

Weekly’s too short for most vol expansion plays. Use monthly options:

Sensex monthly (last Thursday) gives 30+ days for a move to develop
Nifty monthly (last Tuesday) similar

For directional bets

Match your holding period to the expiry:

2-5 day view → weekly (Sensex or Nifty)
2-4 week view → monthly
Longer view → next-month monthly (Indian LEAPS-like options are thin)

For calendar / diagonal spreads

Sell weekly, buy monthly — the classic PMCC-style setup
Keep both legs on the same exchange for cleaner Greeks and margin

The multi-index arb angle

Because Sensex and Nifty now expire on different days, you have:

Different theta profiles on any given day of the week
Potentially arbitrageable IV differences on similarly-correlated indices
More opportunity for cross-index calendar structures

Institutional traders exploit this. Retail can too, if you understand both indices’ behavior.

Event calendar

Certain macro events land on specific weekdays. Know these to avoid selling premium into headwinds:

Event	Typical day	Impact
RBI Monetary Policy	Friday (every 2 months)	🔥🔥 High vol day
Union Budget	1st Feb	🔥🔥🔥 Massive
GST Council meeting	Weekend (quarterly)	🔥 Moderate
US FOMC decision	Wed evening IST (every 6 wks)	🔥🔥 Overnight gap risk
US CPI release	Mid-month, evening IST	🔥 Vol spike
Quarterly earnings peak	Jan/Apr/Jul/Oct	🔥 Stock options only
State election results	Varies	🔥🔥 If large state
General election result	Every 5 years	🔥🔥🔥 Massive

Rule for premium sellers: avoid entering short-vol trades if any 🔥🔥+ event falls within your expiry window. High premium often signals real risk, not opportunity.

Sensex-specific practical notes

Since Sensex is now the top-volume Indian option:

1. Liquidity concentration — most flow is on the current-week Thursday expiry. Off-cycle expiries (monthly beyond current week) have wider spreads.

2. Cross-exchange consideration — Sensex is on BSE, Nifty on NSE. If you trade both, you’re on both exchanges with separate margin pools and separate contract notes.

3. Strike density — Sensex option chain typically has strikes at every 100 points near ATM. Nifty typically at every 50 points.

Bankex — BSE’s banking exposure

Bankex is BSE’s banking index (BSE counterpart to Bank Nifty). Monthly-only after SEBI’s 2024 rationalization.

If you want banking-sector options exposure:

Bank Nifty monthly (NSE, last Tuesday) — more liquid, broader participation
Bankex monthly (BSE, last Thursday) — different day, decent liquidity

The weekly trading calendar (post 01-Sep-2025)

Monday: quiet day; second day of new Nifty weekly cycle; second-to-last of Sensex weekly
Tuesday: Nifty weekly expiry (NSE). Last Tuesday of month = Nifty monthly + all NSE stock/index monthlies
Wednesday: Start of new Nifty weekly cycle
Thursday: Sensex weekly expiry (BSE). Last Thursday of month = Sensex monthly + Bankex/Sensex 50 monthly
Friday: New Sensex weekly cycle starts; RBI decisions often fall here
Weekend: global news accumulates; Monday gap possible

Structure entries and exits around this rhythm.

Which weekly should YOU trade?

Your profile	Best pick	Why
New retail trader, small account	Sensex weekly (BSE)	Top-volume Indian option; tight spreads; Thursday expiry
Nifty preferred, established habits	Nifty weekly (NSE)	Familiar underlying; still highly liquid; Tuesday expiry
Banking sector view	Bank Nifty monthly (NSE)	Larger and more liquid than Bankex
Longer-horizon trader	Monthly Nifty (NSE) or monthly Sensex (BSE)	Both indices have monthly cycles; pick by exchange preference
Individual stock plays	Reliance / TCS / HDFC monthly (last Tuesday, NSE)	Monthly-only; physical delivery — always close before expiry unless taking delivery

Settlement mechanics

Advanced How Indian expiry settlement actually works

The last-30-minute rule

Indian index options settle at the weighted average of the underlying’s last 30 minutes (3:00pm - 3:30pm on expiry day).

Not a single closing print — a VWAP
Prevents last-minute manipulation
Published by exchange ~4:15pm as the “final settlement price”

Implication: in the last 30 min of expiry day, price behavior of the underlying dominates option pricing. Your ATM option can whipsaw 50-100% in the last hour.

Cash vs physical settlement

Index options (Nifty, Sensex, BankNifty, etc.): cash-settled. Difference between strike and settlement price × lot size × moneyness = credited or debited.

Stock options (Reliance, TCS, HDFC, etc.): physically settled. If ITM:

Short call → deliver stock at strike (need margin for delivery)
Long call → receive stock at strike (need cash for delivery)
Similar for puts (short put → receive stock; long put → deliver stock)

The catch: if you don’t have shares/cash to deliver, broker auto-squares your position ~2 days before expiry OR you face auction penalties. Never let ITM stock options ride to expiry unless deliberately taking delivery.

Margin scaling in expiry week

Physical settlement risk causes:

Reliance short call margin doubles on expiry Monday
Reliance short put margin doubles on expiry Monday
Some brokers require 100% delivery-worth cash by Friday before

Zerodha, Upstox, and Angel One all send explicit expiry-week notices. Check them.

STT on expiry ITM

Formula

STT on exercised options = 0.125% × Intrinsic value × Lot size

Example: Nifty 25,000 CALL, spot 25,300, held to expiry:

Intrinsic = 300
STT = 0.125% × 300 × 65 = ₹24 per lot (not bad)

But a deeper ITM:

Intrinsic 1,000, STT = 0.125% × 1,000 × 65 = ₹81 per lot (still OK)

The math only bites when you have MANY lots or extreme moneyness. Still — always close before 3:20pm to avoid.

Expiry-day playbook

Advanced How to trade Indian expiry day itself

9:15 - 10:30 AM (opening & morning drift)

Wide spreads at open — avoid entries
If overnight news, positions gap; ATM options can be up/down 30% at open
Best action: wait 15 min for spreads to normalize; then trade

10:30 AM - 1:00 PM (calm zone)

Best time to close short positions (theta already collected)
Best time to enter new short strangles for NEXT expiry cycle
Theta on current-week options: ~30% of remaining daily decay in this window

1:00 - 2:30 PM (gamma buildup)

Delta acceleration begins for ATM strikes
Volume picks up sharply
Institutional squaring-off pushes underlying around

2:30 - 3:00 PM (max gamma)

ATM options: gamma effectively infinite
Small underlying moves cause huge option price changes
This is where short strangle traders die if not closed already

3:00 - 3:30 PM (settlement window)

Final settlement based on this 30-min VWAP
Do NOT try to trade options here — spreads blow out, pin risk maxes
Close everything by 3:00 pm. Exceptions require experience.

The 3:20 pm cliff

Many brokers auto-square-off retail positions after 3:20 pm if:

Position is naked short with insufficient margin
Physical settlement obligation looming
STT liability approaching

Set your own alerts before broker forces the exit.

Rollovers

If you want to extend a position:

Buy back current expiry (any time)
Simultaneously sell next expiry (bracket order)
Never leave the position half-rolled overnight

Rollover happens between 12 PM and 3 PM typically for large volume.

Expiry-day trading vs. selling premium

Advanced Should retail trade expiry day at all?

The case FOR expiry-day trading

Highest option volume of the week = tightest spreads on ATM
Massive theta decay in the final hours (short options collect fast)
Clear direction post-noon usually — trend continuation trades work

The case AGAINST

Gamma is highest → single 100-point Nifty move can swing a strangle P&L by 50-100%
Fills degrade after 3:00 pm (spreads widen 3-5×)
Emotional pressure amplified by fast P&L swings
Missing an exit means either delivery obligations (stocks) or STT (indices)

The retail rule

Beginners: never hold to expiry day. Close by Monday of expiry week for weeklies; Friday before for monthlies.
Intermediate: OK to enter short strangles on Wed for Sensex, Fri for Nifty (2 days out); close by mid-day expiry.
Advanced: expiry-day scalping with tight stops and pre-defined exits.

The best expiry-day trade for retail

Iron condors, entered 3-5 days before expiry, closed at 50-70% of max profit BEFORE expiry day.

You capture 80% of the theta with 20% of the gamma risk. Almost no expiry-day exposure.

Key takeaways

NSE → Tuesday. BSE → Thursday. One sentence, everything else follows.
Only Sensex (Thursday) and Nifty (Tuesday) have weekly options. Every other product is monthly-only after the 2024 consolidation.
All NSE monthly expiries fall on the last Tuesday — Nifty, Bank Nifty, Finnifty, Midcap Nifty, Nifty Next 50, and all single stocks (Reliance, TCS, HDFC, etc.).
All BSE monthly expiries fall on the last Thursday — Sensex, Bankex, Sensex 50.
Physical delivery on stock options — last Tuesday of month. Close before if you don’t want shares.
Pre-September 2025 references show OLD expiry days. Always verify.