Interactive Brokers (IBKR) has seen total net revenues grow from about $1.4 billion in 2016 to roughly $6.2 billion in 2025, driven by expanding client activity and deposit growth while maintaining higher margins.

The growing customer base pushed revenue and profitability, with cash and margin interest on client balances becoming the firm’s largest revenue source, rising from $527 million in 2016 to over $3.5 billion last year and about $1.06 billion in net interest income in the latest quarter.

Cautionary notes indicate that the extraordinary margin expansion seen previously (55% to 77%) is unlikely to repeat, and the current valuation remains rich at roughly 33 times expected earnings, so future gains depend more on ongoing business growth than on multiple expansion.

IBKR delivered dramatic stock-price appreciation since 2016, with a $10,000 investment turning into about $110,000 over ten years when dividends are reinvested, versus a much larger gain for the S&P 500.

The brokerage shifted to a higher-margin model, exiting the U.S. options market-making business in 2017 and focusing on automated electronic brokerage and market making, which helped pre-tax profit margins rise from 55% in 2016 to 77% in the latest period.

Overall takeaway: IBKR’s decade-long gain was driven by rapid customer growth and rising cash and margin balances, but sustaining similar performance will require ongoing business expansion rather than repeat margin gains or valuation support.

Recent momentum continues, with second-quarter results showing 34% year-over-year account growth and a 30% rise in commission revenue to $673 million, alongside potential uplift from a September rate increase by the Federal Reserve.

The customer base surged nearly 15-fold, from 370,000 accounts in 2016 to 5.46 million by August this year, with cash deposits growing from $82.7 billion to $962.8 billion.