Interactive Brokers Group, Inc.
A 78% margin compounding machine, priced for growth just as rates turn

Research date: 31 October 2026. Company: Interactive Brokers Group, Inc. Listing: Nasdaq Global Select, IBKR. CIK 1381197. ISIN US45841N1072 (derived from CUSIP 45841N107; not read from a filing this run). Reporting currency: USD (US GAAP). Latest financial period reviewed: quarter ended 30 September 2026 (earnings release, 8-K exhibit 99.1, 15 October 2026). The IBKR Mobile capture ran on 31 October 2026 from 15:33 to 15:35 Europe/Luxembourg.

Tags used throughout: confirmed means a company filing, release or other primary source. est. means our own arithmetic from confirmed inputs. speculated means a sell-side, aggregator, transcript or data-vendor figure. Every figure carries the source's own date, and market data and rating rows also carry the capture time.

Idea origination: why we are researching IBKR

Interactive Brokers is on The Claude Trader research list as a large, founder-controlled, highly automated global broker. It also supplies the research app used for the ratings capture in this series. There is no outside thesis to test. The question is the usual one for a broker that earns most of its money on interest: how much of the current growth comes from account growth that will last, how much comes from interest rates that are now falling, and is the price already paying for it? This report is research, not a recommendation.

Investment memo: our current view

This is a quality compounder that our base case values close to the current price. Q3 2026 results (8-K, 15 Oct 2026, confirmed):

• Customer accounts rose 35% to 5.58M.
• Customer equity rose 27% to USD 964.7B.
• Customer margin loans rose 36% to USD 105.2B.
• Net revenues rose 16% to USD 1,914M.
• Pretax margin was 78%.
• Diluted EPS was USD 0.69, up from USD 0.59.
• The quarterly dividend rose 71%, from USD 0.0875 to USD 0.15.

Net interest income was USD 1,154M, about 60% of net revenues (est. from confirmed figures). That is the main sensitivity. On the Q3 call, management put the cost of each 25 bp cut in US rates at about USD 83M of annual net interest income, plus about USD 35M for each 25 bp cut in non-US benchmarks (speculated: third-party transcript, not yet checked against the 10-Q).

At USD 76.90 (30 Oct 2026 close, Yahoo) the stock trades at 28.9x our FY2026E EPS of USD 2.66 (est.). Our scenario values today are USD 48 bust, 83.4 base and 119 boom (est.). The FAIR_VALUE.json average of three inputs is USD 87.6, which sits 13.9% above the price (est.; meter green). The three inputs are:

• Morningstar fair value: USD 75, dated 19 Oct 2026, read via IBKR Mobile.
• LSEG consensus target: USD 104.39, 18 analysts, read via IBKR Mobile.
• Our base case: USD 83.4.

The stock fell from USD 85.33 (21 Oct) to USD 76.90 (30 Oct), including -5.6% on 30 Oct (IBKR quote). We did not find a company-specific cause. The IBKR news feed that day shows a sector move in crypto-linked shares after a reported Binance hack (speculated).

Next hard tests: the October 2026 monthly brokerage metrics, expected around 2 November 2026 (est.), then Q4 2026 results, expected around 20 January 2027 (est., not yet announced).

Thesis underwriting: from source idea to investable conclusion

Listing and timestamps

What the business actually sells

IBKR is an automated global broker. It provides trade execution and custody in securities, commodities, FX and event contracts on more than 175 markets from one platform. Its clients are individuals, hedge funds, proprietary trading groups, advisers and introducing brokers (confirmed, release boilerplate, 15 Oct 2026).

Source: Q3 2026 release, 15 Oct 2026, re-read on EDGAR on 31 Oct 2026. The balance base behind NII at 30 Sep 2026 was customer credits of USD 186.2B (+20%) and margin loans of USD 105.2B (+36%) (confirmed).

Where the account sits: one average account and the money it brings

The cutaway goes from customer equity across the platform down to one average account. The money ladder follows one average account for one year. All per-account figures are est.: Q3 2026 totals (confirmed) multiplied by four and divided by 5.58M accounts. New accounts are smaller and trade less than this average.

Reading. One million new accounts at these averages would bring about USD 1.37B of revenue a year, about 18% of the annualised run rate (est.). The interest line per account is the part most exposed to rate cuts.

The financial starting point

The non-controlling interest (IBG Holdings) takes about 77% of net income (1,034 of 1,348 in Q3, est.). The listed share therefore captures only a slice of each dollar. The P/E on listed EPS is the right measure for the listed share, because EPS is computed on the 26.6% stake.

FY2026E EPS USD 2.66 = 9M actual 1.98 + Q4 est. 0.68 (est.).

Competitors and market share (31 October 2026)

The main peers are Charles Schwab, Robinhood, Futu and UP Fintech (Tiger). Peer client assets and multiples were not captured this run, so we show no share percentages. IBKR's differences are qualitative and confirmed only by its own description: global multi-asset access from a single account, institutional and introducing-broker clients alongside retail, and a cost base built on automation (78% pretax margin, confirmed). A peer table is still open.

Scenarios: FY2027 EPS under bust, base and boom (31 October 2026)

Values are one year forward, not discounted. A 100 bp cut everywhere costs about USD 472M a year (4 x 83 + 4 x 35, est. on speculated inputs). That is about 6% of the annualised revenue run rate, so in the bust case balance growth absorbs most of the cut but not all of it.

Valuation: market data and scenario values as of 31 October 2026

External anchors:

Named broker targets on MarketBeat (speculated, captured 31 Oct 15:05): Barclays 117 (16 Oct), Bank of America 116 (5 Oct), Goldman Sachs 111 (1 Oct), Capital One 105 (6 Oct), Deutsche Bank 104 (16 Oct), Wells Fargo 102 initiation (2 Oct), BMO 100 (16 Oct), Evercore ISI 100 initiation (12 Oct), UBS 97 (20 Oct).

Price versus fair value. The average of Morningstar (75.0), LSEG (104.39) and our base case (83.4) is USD 87.6. That is 13.9% above the USD 76.90 price (est.; meter green). Broker targets are drawn but not averaged, because the consensus already contains them. The price sits just above Morningstar and below our base case. The market is pricing in some rate-driven earnings pressure, but not the bust case.

IBKR ratings

Fair value update (31 Oct 2026, after this capture): the average shown on the price chart is now USD 87.6, 13.9% above the 2026-10-30 close of 76.9 (green). Inputs: Morningstar fair value via IBKR Mobile (Analyst Equity Report; 3 stars, moat Wide, uncertainty High) 75.0 (2026-10-19); LSEG (Refinitiv) consensus target, 18 analysts, via IBKR Mobile 104.39 (2026-10-31); The Claude Trader base case 83.4 (2026-10-31). Where an earlier section quotes a different average, this one is current.

Captured 2026-10-31 15:33 to 15:35 Europe/Luxembourg from IBKR Mobile (atws.app), with a read-only login on the research emulator. Markets were closed, so the quote is the frozen 30 Oct session. The data comes from the company's own app, which redistributes third-party research (LSEG, Morningstar, TipRanks) and does not guarantee it. We note that IBKR is reporting on itself here and treat the rows as vendor data like any other. Full table with screenshots: ibkr/ibkr_ibkr_2026-10-31.md. The read-only app had no short-interest screen.

The ownership row covers the listed Class A shares only. It does not show the 73.4% of IBG LLC held through IBG Holdings. The TipRanks average (106.10) is described in the app as +37.97%, which implies a different reference price from LSEG's +27.66%. Both are vendor computations.

Latest IBKR news (capture 15:35:52): - 30 Oct 2026 IB Market Signals: IBKR price spike down, last 76.91, -4.86 (-5.94%) - 30 Oct 2026 Benzinga: crypto-linked shares lower after a Bitcoin drop on a reported Binance hack (about USD 6.3B) - 30 Oct 2026 Benzinga: Alphabet's worst week since 2011, Intel record crash (market feed) - Zacks: brokers suggest investing in Interactive Brokers

Leadership and governance (31 October 2026)

• Control. IBG Holdings LLC, the founder-controlled entity, owns 73.4% of IBG LLC. The listed IBG, Inc. owns 26.6% (confirmed, Q3 release). Public holders own a minority economic slice and do not have control.
• People. Thomas Peterffy is the founder and Chairman, Milan Galik the CEO and Paul Brody the CFO (speculated: the 2026 proxy was not read this run, so we have no confirmed biographies, pay or Form 4 register). Investor relations contact: Nancy Stuebe (confirmed, release).
• Capital return. The dividend rose from USD 0.0875 to USD 0.15 a quarter (confirmed). Management framed the increase around the dividend framework on the call (speculated, transcript).
• Operational flag. The order-cancellation incident of 25 March 2026 hit the shares (speculated, secondary article; no primary filing read).
• Hard red flags. None found in the material read. Restatement and auditor-change checks were not run systematically this run.
• Revenue quality. About 60% of revenue is interest-driven and moves with policy rates. Commissions depend on retail activity. Stock share volume fell 24% year on year in Q3 while futures rose 13% (confirmed). Other income includes currency-diversification gains (USD 40M in Q3, confirmed), which do not recur in any reliable way.

Fact-audit notes (data-file audit, 31 October 2026)

The audit agent checked 34 claims in the IBKR data files and found nothing wrong. REPORT.md did not exist at audit time, so this report's own figures were re-checked here against the Q3 release on EDGAR.

What is still open

• Rate sensitivity from the Q3 10-Q, rather than from the call transcript.
• The 2026 proxy: leadership biographies, pay and the Form 4 insider register.
• Peer client assets and multiples (Schwab, Robinhood, Futu, UP Fintech).
• The cause of the 21 to 30 Oct 2026 slide from 85.33 to 76.90.
• Systematic restatement and auditor checks.
• A confirmed Q4 2026 report date.

Checkpoints that can change the view

Information dates and future updates

All figures carry their source dates. Prices refresh only on request (see FAIR_VALUE.json). Review again after the October metrics release.

Sources read

• Q3 2026 earnings release, 8-K exhibit 99.1, 15 Oct 2026: https://www.sec.gov/Archives/edgar/data/0001381197/000138119726000154/ibkr-ex99_1.htm
• Same release via Business Wire on Morningstar: https://www.morningstar.com/news/business-wire/20261015881618/interactive-brokers-group-announces-3q2026-results
• Q3 2026 call transcript (third party): https://www.webull.com/news/15760509186237440
• Beancount Q3 2026 analysis, 26 Oct 2026: https://beancount.io/blog/2026/10/26/interactive-brokers-fy2026-q3-earnings-analysis
• MarketBeat price targets, 30 Oct 2026: https://www.marketbeat.com/stocks/NASDAQ/IBKR/price-target/
• Yahoo Finance chart API, IBKR daily closes 31 Jul to 30 Oct 2026
• Rallies.ai on the March 2026 order-cancellation incident (secondary)
• IBKR Mobile capture, 31 Oct 2026: ibkr/ibkr_ibkr_2026-10-31.md and screenshots

Next dated hard test: October 2026 monthly brokerage metrics, expected around 2 November 2026 (est.). After that come the Q4 2026 results, expected around 20 January 2027 (est., not yet announced).