Prediction: Interactive Brokers Ends 2026 With More Than 6 Million Customer Accounts

Interactive Brokers (NASDAQ:IBKR) grew its customer-account count by another 143,000 in August. That put the automated global broker at 5.46 million accounts, up 35% from a year earlier, according to the monthly metrics update it published on Sept. 1.

A total like that puts a round number within reach. And my prediction is that Interactive Brokers gets there, ending 2026 with more than 6 million customer accounts.

The milestone isn't a formality, though. Hitting it requires the last four months of the year to deliver almost as much account growth as the previous four did.

Image source: The Motley Fool.

Running the numbers

Getting from 5.46 million accounts on Aug. 31 to 6 million by Dec. 31 requires growth of about 2.4% a month for four months. That means about 135,000 additions a month.

The company has been running ahead of that bar. It added just over 600,000 accounts in the four months through August (an average of about 150,000 a month) as its total climbed from April's 4.86 million. And August's 143,000 additions alone were already above the monthly average the milestone calls for.

In other words, Interactive Brokers could slow down from its summer pace and still cross 6 million. Every month since April has cleared the required rate.

Can the pace hold?

The growth streak is much longer than a summer. The company entered 2026 with about 4.4 million accounts and has grown its base every month since, at monthly rates of about 2.2% to 3.8% by my math.

Even more, the growth has been speeding up. Customer accounts were 31% higher year over year in February. And by August, the growth rate had reached 35%.

"We are growing everywhere globally, all the regions, all the account types, whether it's financial advisor, introducing brokers, direct accounts," said CEO Milan Galik on Interactive Brokers' second-quarter call in July. "We are pleased with our growth across the board."

Galik also noted momentum with introducing brokers (outside firms that bring their customers onto Interactive Brokers' platform), saying the company had posted probably its fourth or fifth straight quarter with a double-digit number of integrations going online.

Of course, the streak has had slower stretches, and they show how the prediction could miss. From February through April, monthly growth hovered around 2.2% to 2.4%, and four months at the slower end of that range would leave the year-end count just short of 6 million. Last December, account growth was 2% month over month. Four months at that rate would put the total near 5.9 million instead.

Each new account feeds two revenue lines

Each new customer arrives with trading activity and cash. Each feeds one of the company's two main revenue lines.

The trading half shows up as commissions. Commission revenue climbed 30% year over year in the second quarter to a record $673 million, as customer trading volume in options and stocks climbed 17% and 14%, respectively.

The cash half is even bigger. Customers park uninvested cash in their accounts and borrow against their holdings, and Interactive Brokers earns interest on both sides. Net interest income rose 23% year over year to $1.06 billion in the same quarter, mostly because average customer margin loans and credit balances grew. And both balances ended August higher than a year earlier: client credit balances at $185.6 billion, up 27%, and margin loans at $101.5 billion, up 41%.

Sure, one new account may not produce much revenue by itself. But the ones Interactive Brokers keeps adding land on an unusually profitable platform -- the company arguably operates more like a tech company than a traditional broker. It posted a 77% pre-tax profit margin last quarter, up from 75% a year earlier, and earnings per share rose about 35% to $0.69.

Investors haven't ignored any of this. At about $91 as of this writing, the growth stock trades about 7% shy of its 52-week high.

Shares also go for about 28 times next year's earnings estimates -- a price that arguably already assumes the account growth keeps coming.

This prediction is a call on the customer count, though, not a verdict on the stock's valuation. Will Interactive Brokers really finish the year with more than 6 million customer accounts? I think so. The required pace is slower than anything the company has posted since April, and management says the growth is coming from everywhere at once.

A slowdown to last winter's rate would leave the count just short. I just don't see anything in the recent numbers pointing that way.

Daniel Sparks and his clients do not have positions in any of the stocks mentioned. The Motley Fool has positions in and recommends Interactive Brokers Group. The Motley Fool recommends the following options: long January 2027 $43.75 calls on Interactive Brokers Group and short January 2027 $46.25 calls on Interactive Brokers Group. The Motley Fool has a disclosure policy.