On Wednesday 10 Jun 2026 NSE's participant file listed foreign institutions as heavily net short in index futures and the client group as net long by most of that number of contracts. A reel would call that a bearish foreign view and a bullish retail one. The file says something plainer: every long has a short, so someone sits on each side, and the file does not say why. I read it as a ledger first, and as a signal never until it has been tested on dated numbers. This lesson reads the file group by group, says what the FII long short ratio can and cannot show, names who carried the short side of options that day, and runs the dated test. Every figure comes from NSE end of day files, and none is live.

3By the end you can

  1. Read the four groups of the participant file and check that longs equal shorts.
  2. Say what an FII long short ratio counts, and what it cannot separate.
  3. Run a dated test of a positioning claim, and say why overlapping windows overstate it.
Fine teal and blue streamlines flowing across a navy field

The idea, plainly

What the file counts

NSE publishes the file after each close. It splits open contracts into four groups. Client is everyone who trades through a broker and is not in the other three, individuals included. DII is domestic institutions, such as mutual funds and insurers. FII is foreign institutions. Pro is the member firms' own accounts, where dealers and proprietary desks sit among others, and the file does not flag market makers. For each group it gives long and short contracts in index futures, index calls and index puts, and in stock contracts too. The unit is contracts. NSE's option chain counts open interest in units, so divide units by the lot of 65 before you compare the two. The open interest module covers the chain side. The file covers all index contracts together, not Nifty alone.

The ledger rule

Every contract has a buyer and a seller. So for each product the longs of the four groups add up to their shorts, and the net positions of the four groups add up to zero. That is a free check on the file. It also breaks a common reading: when one group is heavily net short, the others are net long by the same total. The arithmetic does not say which side knew more.

Four groups, one ledger: every long is somebody's short

Client, DII, FII and Pro each report longs and shorts; every long has a short, so the net positions of the four groups add up to zeroDiagram with 6 boxes. Client to Every long has a short; DII to Every long has a short; FII to Every long has a short; Pro to Every long has a short; Every long has a short to Net positions add up to zero.ClientBrokers'clientsDIIDomesticinstitutionsFIIForeigninstitutionsProMembers'ownaccountsEvery long has a shortLongs equal shorts, product byproductNet positions add up to zeroAcross the four groups
How the participant file adds up. Longs and shorts are counted for each group and each product, and the totals match. Source: NSE participant wise open interest, end of day file; layout by RupeeCase. As of 10 Jun 2026.

FII held far more short than long index futures, and the client group the reverse

On 10 Jun 2026 the FII group held far more short than long index futures contracts, while the client group held more long than shortClient, long 2,77,954; Client, short 71,591; DII, long 68,620; DII, short 15,031; FII, long 32,698; FII, short 3,04,677; Pro, long 58,510; Pro, short 46,483.Index futures contracts by group, 10 Jun 2026; L is lakhClient, long2.78LClient, short0.72LDII, long0.69LDII, short0.15LFII, long0.33LFII, short3.05LPro, long0.59LPro, short0.46L
Long and short index futures contracts of each group at the close of 10 Jun 2026, all index contracts together. The four long bars add up to the four short bars. Source: NSE participant wise open interest, end of day file (index futures and index options), computed by RupeeCase. As of 10 Jun 2026.

On 10 Jun 2026 the FII short bar is many times its long bar, and the client group's long bar is the larger of its two. DII and Pro are small beside them.

The FII long short ratio, and what it hides

The ratio divides one group's long contracts by its short contracts in a product. For FII in index futures that day the long was a small fraction of the short. It is a snapshot at the close. It moves when the group rolls, hedges or closes a position, not only when it takes a view. The same count holds an index future sold against a basket of shares, a call sold against a holding and a calendar spread. The file gives no reason for any position, so a foreign fund hedging Indian shares looks the same as one betting on a fall.

FII and DII data: a different file

NSE's FII and DII report is not the participant file. It lists, for each day, what these groups bought and sold in the cash market, gross and net, in rupees. It tells you what a group did in shares on one day, and it gives no reason either. A net seller in the cash market can be raising cash, rebalancing or meeting redemptions. Open contracts in derivatives and rupees traded in shares are different things, so do not add them or read them as one number. A claim that uses both should say which file each figure came from, and on which date.

Who are the option sellers?

The next chart shows net option positions by group on the same day. Net short calls sat with FII. Net short puts sat with the client group. Pro was net long in both. So option selling is not one group's business: different groups carried the short side of calls and of puts. The file cannot say which holders were dealers, hedgers or speculators. SEBI's studies of individual traders find that almost all mainly buy options, and the client group holds far more than individuals do, so the two do not line up. Module A18 follows the other side of the trade.

Net short calls sat with FII and net short puts with the client group

Net index option positions on 10 Jun 2026: FII net short calls and net long puts, the client group net short puts, Pro net long bothClient, calls 2,15,246; DII, calls 8,154; FII, calls −2,77,427; Pro, calls 54,028; Client, puts −7,67,837; DII, puts 24,377; FII, puts 5,30,987; Pro, puts 2,12,473.Net contracts in index options, long less short; L is lakhClient, calls+2.15LDII, calls+0.08LFII, calls−2.77LPro, calls+0.54LClient, puts−7.68LDII, puts+0.24LFII, puts+5.31LPro, puts+2.12L
Long contracts less short contracts in index calls and index puts, by group, at the close of 10 Jun 2026. For each product the four nets add up to zero within a contract. Source: NSE participant wise open interest, end of day file (index futures and index options), computed by RupeeCase. As of 10 Jun 2026.

Worked example: a ledger check, then a dated test

First the check. Read the futures chart again. The client, DII and Pro groups are net long, FII is net short, and the three net longs add up to the FII net short to within a contract. A ledger that balances is a file you can trust to be counting what it says. It still does not say why.

When FII held a larger long share, Nifty was higher five sessions later on fewer days

In the window from 1 Jul 2025 to 17 Jul 2026, Nifty was higher five sessions later on fewer of the days when FII held a larger long share than on the other daysFII long share above median 34%; At or below the median 61%; All days in the window 47%.Share of days Nifty closed higher five sessions laterFII long shareabove median34%At or below themedian61%All days in thewindow47%
Every session from 1 Jul 2025 to 10 Jul 2026, each read against the close five sessions later, split at the median of FII's long share of index futures (long divided by long plus short). Counts are days, and the windows overlap. Source: NSE participant wise open interest and NSE index close, end of day files, computed by RupeeCase. As of 17 Jul 2026.

The test window is one stretch, and the index ended it lower than it began

Nifty daily close from 1 Jul 2025 to 17 Jul 2026, lower at the end than at the startNifty 50: from 25,542 at 1 Jul 2025 to 24,334 at 17 Jul 2026, high 26,329 at 2 Jan 2026, low 22,331 at 30 Mar 2026.23,00024,00025,00026,000Jul 2025OctJan 2026AprJul24,334
Nifty daily close, 1 Jul 2025 to 17 Jul 2026. The test covers a single regime, not every kind of market. Source: NSE end of day data, computed by RupeeCase. As of 17 Jul 2026.
Read 2 more paragraphs, 198 words

Now the test the question page promised. The rule is set before looking at the result. Each day, take FII's long share of its index futures: long divided by long plus short. Split the days at the median of the window. For each day note whether Nifty closed higher five sessions later. Count both groups. The days run from 1 Jul 2025 to 10 Jul 2026, every session in the files, so the last five session look ends on 17 Jul 2026. It stops there because newer data is too recent for a dated lesson.

Read it with care. The folk reading did not hold in this window. On the days FII held a larger long share, Nifty was higher five sessions later less often, not more. But the window is one stretch, and the index fell over it. Each window shares four of its five sessions with the next, so only about one in five is an independent look. A gap this size across so few independent looks is not strong evidence either way. It shows how to test a claim. It is not a rule to use. The participant data question page has the short version.

The common mistake

The claim: The FII long short ratio is out today, so when foreign institutions are net long the market is about to rise. The ratio counts one group's open contracts, hedges and spreads included. The ledger says the other three groups hold the opposite side by the same total, so the ratio cannot pick the group that is right. And in the dated test above, a higher FII long share was followed by fewer rises over five sessions, not more. Treat the ratio as positioning data. Before trusting it, ask for a test on many dated days, counted both ways, with the overlap admitted.

Key takeaways

  • The participant file counts contracts for four groups: Client, DII, FII and Pro.
  • Every long has a short, so the four groups' net positions add up to zero.
  • An FII long short ratio is one group's count, hedges and spreads included.
  • The file shows positions at the close, never the reason behind them.
  • FII and DII cash flows are a different series, in rupees.
  • A claim about a ratio needs a dated test, counted both ways.

3 terms this section turns on

3 terms this section turns on3 terms this section turns on. Pro: The member firms' own accounts. Dealers and proprietary desks sit here among others, and the file does not flag market makers. Net position: Long contracts less short contracts of one group in one product. Across the four groups the nets add up to zero. FII long short ratio: One group's long contracts divided by its short contracts in a product. It is a closing snapshot that mixes hedges, spreads and views.ProThe member firms' own accounts. Dealers andproprietary desks sit here among others, andthe file does not flag market makers.Net positionLong contracts less short contracts of onegroup in one product. Across the four groupsthe nets add up to zero.FII long short ratioOne group's long contracts divided by itsshort contracts in a product. It is a closingsnapshot that mixes hedges, spreads and views.
From the module glossary; every term is in the Learn glossary too. Source: Module 15.6, Participant wise OI and FII derivatives data, read honestly.

Before you trade. Derivatives trading carries a high risk of loss. SEBI's study "Profitability of Individual Traders in the Equity Derivatives Segment (FY25 to FY26)" (August 2026) found that 87.7% of individual traders in equity F&O made net losses in FY26, with aggregate net losses of Rs 91,685 crore. Read the SEBI study