Interactive Brokers Grew Its Customer Accounts 34% in a Year. Here's the Bull Case Before Q2 Earnings.

Interactive Brokers (NASDAQ: IBKR) is one of a handful of large discount brokerages, competing with the likes of Charles Schwab (NYSE: SCHW) and Robinhood (NASDAQ: HOOD). Competition in the discount-broker space is typically pretty fierce. However, Interactive Brokers has been doing pretty well, if its June 2026 brokerage metrics are any indication. Here's what you need to know.

Interactive Brokers' June numbers were great

In June, Interactive Brokers had 5.185 million client accounts, up 34% from the same month of 2025. Its clients had equity of $930.3 billion in June, 40% higher than the year-ago period. In other words, the company's business has grown materially over the past 12 months. That's very good news, but not the end of the data the company provided.

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For example, Interactive Brokers handled 5.269 million trades in June, an increase of 53% over the prior year. Although the company only makes a few dollars per trade, the more trades it handles, the more commission revenue it generates. On top of that, the discount broker ended June with margin loan balances of $108.5 billion, a huge 67% increase from June 2015. Margin loans generate interest income for Interactive Brokers, so higher balances are also a very positive outcome.

Interactive Brokers' second-quarter earnings could be very good

If that was how the company ended June, it seems highly likely that its second-quarter 2026 earnings update will see a notable improvement over the prior year. That would actually be a follow-up to the financial company's strong first-quarter showing. Some numbers will help.

Interactive Brokers' first-quarter 2026 revenues came in at $1.67 billion, up roughly 17% from $1.43 billion in the prior year. Adjusted earnings increased by roughly 28%, hitting $0.60 per share. The company's commission revenue increased 19%, and its interest income, largely from margin loans, increased 17%.

The company's June numbers weren't materially higher than May's, suggesting the second quarter won't be materially different from the first. However, given the large year-over-year increase in account size, trading activity, and the total margin loan balance, second-quarter earnings seem likely to be much improved over the second quarter of 2025.

There's one small problem with Interactive Brokers

All of that said, investors need to take these numbers with a grain of "valuation salt." The stock's price-to-sales, price-to-earnings, and price-to-book value ratios are all around twice their five-year averages. In other words, Wall Street is well aware of how strongly Interactive Brokers' business is performing. If the company doesn't live up to what are likely to be lofty expectations, even a strong quarter on an absolute basis could still lead to a stock decline.

Charles Schwab is an advertising partner of Motley Fool Money. Reuben Gregg Brewer has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Interactive Brokers Group. The Motley Fool recommends Charles Schwab and recommends the following options: long January 2027 $43.75 calls on Interactive Brokers Group, short January 2027 $46.25 calls on Interactive Brokers Group, and short September 2026 $95 calls on Charles Schwab. The Motley Fool has a disclosure policy.