India's market regulator is about to do something it rarely does: back down.

Reuters reported on October 5 that SEBI will partly reverse its overhaul of how closing prices are struck for derivatives. The Closing Auction Session (CAS) — live in the cash market for F&O-eligible stocks since August 3, 2026 — will stop setting derivatives settlement prices for at least a year. Derivatives revert to the volume-weighted average price of the last 30 minutes of trading. The cash market keeps the auction. SEBI took in roughly 20,000 consultation responses and targets implementation by end-October.

The instinct is to call this a relief trade for brokers. That's half right, and the filings show which half.

One caveat up front. CAS is eight weeks old and no filing in the Xaro corpus mentions it — disclosures run through Q1 FY27. What filings do show precisely is how much of each intermediary's revenue sits in the segment being reverted versus the one keeping the auction. That split is the whole trade, and it is wildly uneven.

Angel One: the purest derivatives bet on the exchange

Angel One has spent three years disclosing exactly how concentrated it is. F&O contributed 87% of gross broking revenue in Q4 FY23, and 84–85% through FY24, per its transcripts and investor presentations.

Then the earlier rounds of SEBI tightening bit. By Q4 FY25 management disclosed that F&O's share of gross broking income "reduced to approximately 77%... as compared to its range of 81% to 87%" — and that gross broking revenue "degrew by 22.6% sequentially to nearly ₹6.3 billion," with total gross and net revenues down 16.3% and 15.7% QoQ. Gross broking was still about 60% of total gross revenue.

So roughly three-quarters of Angel One's largest revenue line sits in the segment SEBI just reverted — no listed broker is more levered to derivatives mechanics. Recovery is visible (Q3 FY26 gross income +11.1% QoQ to about ₹13.4 billion), but the exposure cuts both ways.

BSE: the reverted segment pays the bills; the retained one is shrinking

This is the part nobody is saying out loud.

BSE's FY26 investor presentation puts consolidated transaction charges at ₹13,110 million in the March 2026 quarter against ₹6,117 million a year earlier — more than double, and a jump from 66% to roughly 80% of consolidated quarterly revenue.

Now look at the cash market, which keeps the closing auction. BSE's equity cash transaction charges income was ₹2,495 million for all of FY26, down from ₹3,018 million in FY25 — a 17% decline, even though cash average daily turnover edged up from ₹77,666 million to ₹79,500 million. The segment SEBI retained the new mechanism for earned BSE less in FY26 than the year before, and less across twelve months than its total transaction-charge line earned in the March quarter alone.

Derivatives carried everything: average daily premium turnover in equity derivatives went from ₹4 crore in FY23 to ₹2,133 crore in FY24 (FY24 annual report), and management reported a "highest ever average daily premium turnover of Rs. 8,758 crores" in a FY25 quarter. For BSE, the reverted rule governs the growth engine; the retained rule governs the rump.

SMC Global: the filing that names the culprit

Most companies hedge. SMC Global's FY26 annual report does not. It attributes its profit contraction to "a marked softening in derivatives activity and the consequential impact of regulatory changes introduced in the Futures & Options (F&O) segment," which "exerted pressure on the higher-margin components of the Company's revenue mix" — "the extraordinary regulatory transition that characterised the F&O segment during the year."

The arithmetic in that report shows the squeeze: consolidated revenue from operations rose 5.7% to ₹1,876.9 crore in FY26 while total expenses rose 9.8% to ₹1,750.0 crore. Revenue grew; profit did not.

And SMC is not a derivatives pure-play — management pegged derivative brokerage at "around 38%" against cash at "around 60%" in a 2024 call. If 38% does that to profits, the read-through to Angel One's 77% is obvious. SMC has since recovered: Q4 FY26 operational income of ₹516.9 crore (+22.6% YoY), and Q1 FY27 PAT of ₹36.7 crore against ₹30.0 crore.

IIFL Capital: the diversification that actually worked

IIFL Capital's April 2025 call quantified damage and offset in one breath. March 2025 quarter revenue fell about 20% YoY, from ₹704 crore to ₹573 crore, "primarily due to fall of exchange volumes due to tightening of norms for derivatives expiry." Retail brokerage dropped from ₹194 crore to ₹117 crore; institutional and banking revenue fell from ₹215 crore to ₹97 crore.

But distribution income rose about 62%, from ₹117 crore to ₹190 crore, and FY25 PAT still climbed roughly 40% to ₹713 crore. The derivatives line got hit; the company didn't.

5paisa and CDSL: the chart and the control group

5paisa's FY26 presentation carries a slide titled "Impact of Regulatory Changes on Industry," labelling each shock in sequence — transaction income elimination, weekly expiry limitation, lot size revision. Its client acquisition troughed at 0.78 lakh in Q3 FY26 before rebounding to 1.03 lakh in Q4 FY26.

CDSL is the control group. Its revenue lines are annual issuer charges, transaction charges, IPO and corporate action charges and online data charges — annual issuer charges grew 12.3% YoY as of its August 2026 call. A depository does not care how a settlement price is computed.

What retail investors should do

Separate the signal from the sentiment. This is a mechanism change, not a volume stimulus. SEBI is not restoring the weekly expiries, lot sizes or position limits that actually compressed F&O activity, and nothing in these filings suggests it intends to. Anyone pitching this as the end of the derivatives crackdown is overreading a 30-minute VWAP.

What it does signal is that SEBI will retreat under evidence, which lowers the tail risk of further tightening. Price that into names whose filings show real derivatives dependence — Angel One at roughly 77% of gross broking revenue, BSE at about 80% of revenue from transaction charges — not into depositories or diversified financials where the exposure isn't there. Then use disclosure as your screen: Angel One, SMC Global and IIFL Capital publish segment splits quarterly. Read the Q2 FY27 numbers when they land, the first to cover the CAS period.

Data sourced from company filings on NSE via Xaro.