The Expiry Week Playbook: NIFTY and BankNIFTY

Calendar checked on 16 September 2026: NSE specifies Tuesday for NIFTY weekly expiry and the last Tuesday for monthly expiry. BANKNIFTY has monthly and quarterly contracts. Holidays move expiry to the previous trading day. Use the selected contract's date, not a remembered weekday.

Consider an illustrative expiry session at 1:45 PM. NIFTY is sitting 30 points above a round strike with concentrated open interest. The chart shows support below, while price has been moving sideways for an hour. A later decline toward max pain could be consistent with positioning, but would not prove positioning caused the move.

Expiry can change time decay, liquidity, and hedging sensitivity. Open interest and gamma estimates add context to the chart. They do not guarantee a range, a direction, or a settlement price. The examples below are illustrative, not dated market records.

A positioning map can become stale between the opening sessions of a contract cycle and expiry. Checking once and treating it as fixed misses changes in open interest, the estimated gamma regime, and price.

A useful sequence is to establish a baseline several sessions before expiry, compare changes during the intervening sessions, and reassess immediately before and during expiry. For a normal Tuesday NIFTY expiry, the preceding trading session is Monday; holidays can change this sequence.

Checking each of these data points individually is possible but fragmented. You open the NSE option chain, scroll through strikes, try to remember where OI was yesterday, then switch to a GEX calculator, then back to your chart. By the time you have a picture, the picture has changed.

Multi-dimensional synthesis brings the OI landscape, the gamma estimate, and price context into one read. Check which observations are available and when they were updated. The trader still decides how much weight to give each interpretation.

The method that follows teaches the day-by-day sequence.

Step 1: Several sessions before expiry — map the OI landscape

Pull the option chain for the selected contract. Identify where put and call OI are concentrated. These concentrations are often called put and call walls. Treat them as reference levels, not an established floor and ceiling.

Next, locate max pain, the settlement price that minimizes the aggregate intrinsic payout on outstanding options under the calculation's assumptions. It is a positioning reference, not a forecast of where price will settle.

Finally, note the estimated gamma regime and how the source calculates it. A positive dealer-gamma estimate is consistent with stabilizing hedging; a negative estimate is consistent with amplifying hedging. Open interest alone does not establish every dealer's actual position.

Keep the contract and source timestamp with this baseline so subsequent comparisons refer to the same expiry.

Step 2: Intervening sessions — check for positioning shifts

Compare the latest OI distribution with the baseline. Has max pain moved? Have put or call concentrations shifted? Has OI increased at a previously quiet strike?

A shift is evidence that positioning has changed. Its importance depends on the size of the change relative to the contract's recent activity; the number of strikes alone does not establish institutional intent.

Open interest records outstanding contracts, each with a buyer and a seller. Compare OI changes with premium, price, and flow rather than assuming a call or put buildup is automatically directional.

Step 3: The preceding trading session — review the latest evidence

For a normal Tuesday expiry this checkpoint is Monday. Positioning can still change after this checkpoint; the closing chain does not determine the next session's settlement.

Check whether put and call concentrations have moved closer together, whether volume is unusual relative to normal activity, and whether premium flow agrees with price.

Large prints can reflect hedges, spreads, rolls, or directional exposure. Record competing interpretations where the available data cannot distinguish them.

Step 4: Expiry morning — reassess gamma and price

Near-the-money options can become more sensitive to small price changes as expiry approaches. The effect depends on moneyness, volatility, and time remaining, so recheck the current estimate.

Recheck the gamma regime against the observed price response. A positive estimate may support a range-bound interpretation; a negative estimate may support wider moves. Neither selects a trading strategy by itself.

If an estimated gamma flip lies near price, note how the interpretation would change on either side and whether current flow supports that interpretation.

Step 5: Expiry afternoon — update the interpretation as contracts close

Time value, liquidity, and open interest can change quickly in the final hours. Earlier observations may no longer describe the selected contract.

Compare the latest premium, OI concentrations, and gamma estimate with the morning read. Positions may close or roll to another expiry, changing which levels matter.

Keep max pain as one reference among several. A move toward it is possible, but settlement elsewhere is also possible. Price and flow remain relevant throughout the session.

Illustrative example, not a historical market record: several sessions before a Tuesday NIFTY expiry, price is 23,180. Put OI is concentrated at 23,000, call OI at 23,300, and max pain is 23,150. The dealer-gamma estimate is positive. These are reference points for a range scenario, not a promised outcome.

By the preceding Monday, put OI is concentrated at 23,100 and additional call OI appears at 23,250. Max pain has shifted to 23,200. A large call print could reflect a hedge or a directional position; the print alone does not distinguish them.

On Tuesday morning, price moves between 23,180 and 23,260. That observed behavior is consistent with the range scenario. A break accompanied by conflicting flow or a changed gamma estimate would weaken it.

Suppose price later reaches 23,195. That outcome would be consistent with the earlier map, but it would not validate the method's predictive accuracy. A different session could resolve outside the same apparent boundaries.