Interactive Brokers' Q3 2026 net interest income faces a key test with results due after the close on October 15. Analyst consensus targets $1.12 billion, up from $967 million in Q3 2025 and following Q2 2026's $1.06 billion. Growth stems primarily from 36% year-over-year expansion in client margin loans to $105.2 billion and 20% higher credit balances at $186.2 billion as of September, outweighing a modest net interest margin compression to around 1.93%. Rising client equity to $964.7 billion and account growth to 5.58 million further bolster average interest-earning assets near $240 billion. Lower sequential DARTs may pressure commissions, but balance-sheet expansion remains the dominant positive driver for NII relative to historical quarterly trends.