Gap Fill Strategy for Nifty and Stocks

A gap fill strategy considers trades toward the previous session’s closing price after the market opens above or below it. In this guide, a full fill means touching that prior close during the defined observation period; a partial fill means recovering only part of the opening distance. Gaps can remain unfilled. No verified Nifty or Bank Nifty fill-rate dataset is provided here, so there is no claimed win rate.

Opening gap, full gap and full fill are different terms

For an opening-gap measurement, compare the current session’s open with the previous session’s close. A positive difference is a gap up; a negative difference is a gap down. This measurement can exist even when the open is inside the previous day’s high-to-low range.

StockCharts’ gap-trading documentation distinguishes a full gap up, which opens above the previous high, from a partial gap up within the earlier range. The downside distinction uses the previous low. Those labels describe where the gap begins. A full fill describes whether the later move reaches the chosen reference price.

Choose the fill reference before reviewing the outcome. A return to the previous close, a move into the previous range and a return to the opening price of another session are different events. Switching between them after looking at the chart can make a result appear more successful than the rule actually was.

The four types of price gaps

Traders often sort gaps into four labels. The labels describe what the gap turned out to mean, so you usually cannot be sure of the type at the open. StockCharts says the distinction becomes clear only after later price behaviour.

StockCharts also uses a simpler split. A full gap opens beyond the previous day's high or low. A partial gap opens beyond the previous close but inside the previous range. It says full gaps generally trend farther in the gap's direction, while partial gaps tend to retrace more quickly. For partial gaps it suggests tighter trailing stops of about 5-6%. Treat these as that source's guidance, not a tested rule for Nifty.

Define the hypothesis before testing entries

A gap-fill idea expects price to move back toward the previous close. A continuation idea expects price to keep moving in the direction of the opening gap. Neither follows automatically from the mere existence of a gap. Record what would count as evidence for the particular rule being examined and what would invalidate it.

• State the instrument, price series and regular-session boundaries. Keep the cash index, futures contract and option-premium chart distinct.
• Mark the prior close, prior high and low, and the current open. State whether any corporate-action adjustment is involved.
• Specify the observation window and fill reference. A same-session test is different from waiting indefinitely.
• Write a hypothetical entry condition, stop condition and time exit before inspecting later candles.
• Keep eligible observations where the entry condition never occurred separate from executed trades.

Common, breakaway, continuation and exhaustion are descriptive gap categories. StockCharts cautions that the distinction becomes clear only after subsequent price behaviour. Labelling a gap as exhaustion after seeing its reversal and then treating that label as information available at entry introduces hindsight into the rule.

The gap-up and gap-down guide covers opening context. For a range-based rule, the opening-range guide explains the early-session high and low. An opening range is a chosen starting interval; this article does not claim an optimal interval for Nifty.

Fade the gap vs gap and go

A fade bets that the gap will shrink. After a gap up, you would sell once buying pressure fails; after a gap down, you would buy once selling pressure fails. Gap and go follows the gap direction. StockCharts describes a version that waits for a rebound with volume of at least twice the 5-day average and says it suits experienced traders with fast execution. For a partial gap without enough volume, it suggests waiting for a break of the previous high or low.

• Fade rule set: a written trigger such as a completed bar closing back toward the previous close, a stop beyond the opening extreme, and a target at the previous close or part of the way there.
• Gap-and-go rule set: a written trigger such as a break of the early-session high (see the opening range breakout), a stop below the opening-range low, and a trailing exit.
• Both need a time exit, so a trade that goes nowhere does not stay open all day by habit.
• Fading a gap up means selling first. Check which products your broker lets you sell first before you plan it.

Neither approach is better in every market. The journal can show which one your own records support: tag each trade as fade or gap and go and compare. See also how to trade gap up and gap down.

Setting targets: full fill vs partial fill

Many traders aim for part of the gap, because price often stalls before the previous close. The cost is a worse reward-to-risk ratio. Using the fictional stock from the example above (previous close ₹1,000, open ₹980, entry ₹985, stop ₹975), a half-gap target of ₹990 gives reward of 990 − 985 = ₹5 against risk of ₹10, a ratio of 0.5. The full-fill target of ₹1,000 gives 1.5.

A ratio of 0.5 needs a high win rate to break even before costs. Use the win rate and reward-to-risk breakeven calculator to see how high. Write the target rule in your plan before the trade, and record whether you followed it.

Where to place the stop

Common choices are beyond the opening extreme, beyond the high or low of the entry bar, or at a fixed percentage. Each gives a different risk per share. A wider stop reduces the chance of being shaken out but cuts the reward-to-risk ratio, or forces a smaller quantity. Choose one rule and keep it for the sample you are studying.

Worked example: a fictional stock gap

Assume an unnamed stock previously closed at ₹1,000 and opens at ₹980. These are made-up prices. The opening difference is 980 − 1,000 = −₹20, or −2% of the previous close. The selected full-fill reference is ₹1,000. A later illustrative price of ₹990 has recovered ₹10 of the ₹20 opening distance, which is a 50% partial fill.

For an educational trade calculation, assume a rule that permits a long entry only after a completed bar closes back above ₹985. For the arithmetic, assume price later returns to ₹985 and an entry executes there after that bar has closed. Use an assumed stop level at ₹975 and exit at the prior-close reference of ₹1,000. These are illustrative conditions and execution assumptions, not a tested setup or current trade recommendation.

• Planned price risk per share = 985 − 975 = ₹10.
• Distance from assumed entry to the full-fill exit = 1,000 − 985 = ₹15.
• Illustrative reward-to-risk ratio = 15 ÷ 10 = 1.5.
• For a made-up quantity of 20 shares, a full-fill exit at the assumed price gives (1,000 − 985) × 20 = ₹300 gross profit.
• A stop exit at the assumed ₹975 gives (985 − 975) × 20 = ₹200 gross loss.

The opening gap was ₹20, but the distance from the assumed entry to the prior close is only ₹15. Using the entire gap distance as the trade’s reward would overstate this example. Brokerage, statutory charges and execution differences change the actual result. Costs depend on the trade and broker.

A gap can fill after a trade has already lost

Continue the fictional path: entry occurs at ₹985, price falls to the ₹975 stop, and only later reaches ₹1,000. The opening gap has filled by the declared reference, while the example trade has already exited at a gross loss of ₹200 under its assumed stop execution. Counting that day only as a successful fill hides the loss.

Likewise, a partial fill can occur without satisfying the entry rule. A daily high and low show that certain levels were reached, but may not reveal the order in which entry, stop and exit occurred. When a bar includes both stop and exit levels, the result needs finer observations or a declared conservative handling rule.

The risk-reward calculator helps compare chosen distances. A favourable ratio is a relationship between assumed outcomes, not evidence that those outcomes occur often enough to produce a positive net result.

The Indian open is price discovery

NSE’s equity pre-open documentation says an equilibrium price is selected using executable volume and order-imbalance rules. When a price is discovered there, it becomes the day’s opening price; if no price is discovered, the first normal-market trade supplies the open. The opening level is therefore a market price-discovery result, not an obligation to return to the prior close.

A pre-open indication can also change before the opening price is final. Keep the price you actually used and its observation stage in a study. Read the pre-open session explanation for context. This guide avoids estimating the final cash-market opening price from an overseas futures quote.

Finding gap stocks in the NSE pre-open

NSE runs a pre-open session before the normal market. Indicative prices from that session let you compare each stock with its previous close and list the larger gaps before 9:15. The exact order-entry and matching windows have been revised more than once, so read NSE's current notice for the timings rather than relying on an older article. The final opening price comes only after the session ends.

• Compare the indicative pre-open price with the previous close to get the gap in rupees and percent.
• Note the traded quantity. A large gap on thin pre-open volume may mean little.
• Write the list down before the open, with the rule you will apply to each stock. Add nothing after you see the first candles.
• Check for news, results or corporate actions that explain the gap. Those gaps may not behave like a common gap.

OneTradeJournal has no market data, so it cannot build this list. You get prices from NSE, your broker or a charting site, then log the trades you take by hand.

Gap up vs gap down

The two directions are mirror images in the maths but not always in practice. A gap-down fade means buying into weakness, and a gap-up fade means selling first. Position limits, product types and your own comfort differ for each. Keep gap-up and gap-down trades in separate rows of your journal so mixed results do not hide a direction that works or fails for you.

Why index points cannot stand in for option profit

A Nifty or Bank Nifty gap is measured on the selected index series. An option position earns or loses money from changes in its own premium and quantity. The Options Industry Council’s pricing guide lists underlying price, strike, time to expiry and implied volatility among the premium drivers. A move in the index alone does not specify the option’s exit premium.

To review an actual options trade around a gap, retain the contract, expiry, quantity and actual entry and exit premiums. Compute the premium difference separately from the underlying move. The option-premium guide explains this distinction. The stock-share example above cannot establish the result of an options trade.

What a credible fill-rate study must disclose

• The exact dataset, instrument, date range and session boundaries.
• The definition of an opening gap and the minimum change included.
• Whether the fill reference is a prior close, adjusted prior close or prior-range edge.
• The observation deadline and treatment of holidays, missing data and corporate actions.
• The number of eligible gaps, entries and fills, with gap directions kept identifiable.
• For trade returns, the entry, stop and time-exit rules, ordering of touches, costs and execution assumptions.

Without those details, a percentage labelled gap-fill probability cannot be transferred reliably to a different instrument or entry method. This guide supplies no historical probability estimate. The useful research question is whether a clearly defined rule survives costs and its losing paths, rather than whether a gap eventually disappears.

Gap fill strategy: pros and cons

• Pro: a clear reference level, the previous close, so targets and stops are easy to write down.
• Pro: a short window, usually the same session, so each test is quick to review.
• Pro: works with simple tools; you only need the previous close and the open.
• Con: many gaps keep going. A breakaway gap on news can leave the previous close far behind.
• Con: the stop can be hit before the fill, as the example shows.
• Con: costs and slippage eat into small targets such as a half gap.
• Con: gap types are known only in hindsight.

So is it profitable? No source on this page gives a verified fill rate or profit figure. Whether it works for you depends on your rules, costs and discipline. Test it on your own logged trades. The trading journal guide explains what to record.

Sources

• StockCharts: gap definitions and hindsight in gap categories (checked 15 October 2026).
• NSE: equity pre-open price discovery (checked 15 October 2026).
• Options Industry Council: option-premium drivers (checked 15 October 2026).