Oct 16 (Reuters) - Trading platform Interactive Brokers ( IBKR )

reported a rise in third-quarter profit on Thursday, as

its interest income benefited from higher average customer

margin loans and credit balances.

U.S. brokerages have been actively lending money to clients

for trading and earning interest on idle client cash by

investing it in short-term instruments.

The Fed's September rate cut is also expected to pressure

brokers' net interest income - the difference between interest

earned on assets and interest paid on liabilities - starting in

the fourth quarter.

But further rate cuts would increase margin trading volumes,

boosting commission revenues.

Net interest income rose 21% to $967 million for the

quarter, owing to higher average customer margin loans and

credit balances.

Commission revenue surged 23% to $537 million, driven by a

67% jump in customer stock trading volumes in the three months

ended September 30.

Daily average revenue trades, or DARTs, which represent the

average trades per day generating commissions or fees, rose 34%

in the quarter to 3.62 million from a year ago.

Customer accounts rose 32% to 4.13 million in the third

quarter.

The Greenwich, Connecticut-based company allows customers to

buy and sell stocks, options, futures, cryptocurrencies, bonds,

mutual funds, ETFs and precious metals.

Interactive Brokers ( IBKR ) partners with third-party cryptocurrency

service providers who handle the actual buying, selling and

safekeeping of digital assets.

The trading platform replaced Walgreens Boots Alliance

in the equities benchmark S&P 500 in August.

The automated electronic broker reported a profit of $1.31

billion, or 59 cents per share, for the third quarter, compared

to $909 million, or 42 cents per share, a year ago.