Interactive Brokers Group (NASDAQ: IBKR) delivered a strong quarter, but the composition of the beat matters more than the headline. Net revenue hit $1.90 billion, nearly $100 million above the $1.80 billion consensus. Diluted EPS of $0.69 cleared the $0.64 estimate by almost 8%. The 28% year-over-year revenue growth was powered by two engines: a 30% surge in commission revenue to $673 million and a 23% jump in net interest income to $1.06 billion.
The commission story is straightforward. Customer options volume rose 17%, stock trading increased 14%, and total DARTs climbed 36% to 4.82 million. Options carry higher per-trade revenue than stocks, so the 17% volume growth in options contributed disproportionately to the 30% commission increase. Commission per cleared commissionable order held essentially flat at $2.64. The revenue growth was pure volume, not pricing power. A healthy sign for sustainability.
Net interest income tells a more nuanced story. The 23% growth masks a compression in net interest margin, which fell to 1.93% from 2.07% a year ago. The driver was balance sheet expansion, not rate leverage. Average customer margin loans surged 59% to $96.6 billion, and customer credit balances rose 32% to $171.7 billion. IBKR is earning less per dollar on both sides of the ledger, but the sheer volume of dollars flowing through the platform more than compensated. The standout number: a 67% jump in period-end margin loans to $108.5 billion. Clients are levering up aggressively, which carries both upside and risk.
Customer bad debt expense rose to $10 million from $1 million a year ago. That's a rounding error against $1.46 billion in pretax income, but the tenfold increase is worth watching. If margin loan growth is accompanied by rising credit losses, the NIM compression story gets worse.
Pretax profit margin expanded to 77% from 75%. Revenue growth outpaced a 17% rise in non-interest expenses. Execution, clearing and distribution fees rose 22% to $142 million, driven largely by a $19 million increase in regulatory fees tied to the SEC Section 31 transaction fee rate increase. That's a pass-through cost, not an operational inefficiency. Employee compensation rose 12% to $182 million, reasonable for a firm adding accounts at a 34% clip.
Account growth is a powerful lead indicator. Customer accounts reached 5.19 million, up 34% year over year, and customer equity hit $930.3 billion, up 40%. IBKR is capturing market share in a consolidating brokerage landscape. The organic acquisition cost appears low given the fixed-cost nature of its platform. The 77% pretax margin is evidence of that operating leverage.
The board declared a quarterly dividend of $0.0875 per share, unchanged. No buyback was announced. The company did not provide forward guidance. The absence of a capital return expansion despite the beat is a signal that management sees better uses for cash, or simply prefers to maintain flexibility.
The analytical takeaway: this quarter's beat was real and broad-based, but the NIM compression and the spike in margin loan balances create a tension. IBKR is growing fast and profitably, but the growth is increasingly reliant on clients borrowing more money at lower spreads. If the rate cycle turns or credit quality deteriorates, the margin leverage works in reverse. For now, the volume story is strong enough to carry the quarter, but the next few quarters will test whether the NIM stabilizes or continues to erode.