June 20, 2019

Paul J. Brody
Chief Financial Officer
Interactive Brokers Group, Inc.
One Pickwick Plaza
Greenwich, Connecticut 06830

       Re: Interactive Brokers Group, Inc.
           Form 10-K for Period Ending December 31, 2018
           Filed February 28, 2019
           Form 10-Q for Period Ending March 31, 2019
           Filed May 9, 2019
           CIK 0001381197

Dear Mr. Brody:

       We have limited our review of your filing to the financial statements
and related
disclosures and have the following comments. In some of our comments, we may
ask you to
provide us with information so we may better understand your disclosure.

       Please respond to these comments within ten business days by providing
the requested
information or advise us as soon as possible when you will respond. If you do
not believe our
comments apply to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to these comments, we may have additional
comments.

Form 10-K for the period ending December 31, 2018

Results of Operations
Year Ended December 31, 2018 compared to the Year Ended December 31, 2017
Interest Income and Interest Expense, page 45

1.    We note that your disclosure of net interest income on pages 47 and 52
for the fiscal 2016-
      2018 periods does not agree with the "net interest income" amounts
disclosed in the table
      on page 48. Please advise and revise in future filings, to provide
additional information
      addressing the reasons for the differences in the "net interest income"
amounts disclosed
      for the periods presented. The impact of any adjustments made in
determining the net
      interest margin should also be addressed.
Form 10-Q for the period ending March 31, 2019
 Paul J. Brody
Interactive Brokers Group, Inc.
June 20, 2019
Page 2
Management's Discussion and Analysis of Financial Condition and Results of
Operations
Financial Overview, page 40

2.       We note that you recognized, during the quarter ended March 31, 2019,
an aggregate loss
         of $42 million, due to the stock price decline of a security listed on
a major U.S.
         exchange and the inability to liquidate customers' positions which
were obtained through
         margin loans.

         Please advise and revise in future filings, to address the following:

             Disclose whether the gross amount of the loss was $42 million or
if this amount was
             reflective of any debt collections or liquidated collateral;
             Disclose the amount of subsequent debt collections which have
occurred since the end
             of the quarter; and
             Disclose how collateral requirements are evaluated and adjusted
during a trading day
             to compensate for potential liquidation and credit risks when
there this is no liquid
             market and there is the existence of margin loans exist.

       In closing, we remind you that the company and its management are
responsible for the
accuracy and adequacy of their disclosures, notwithstanding any review,
comments, action or
absence of action by the staff.

       You may contact Michelle Miller at 202-551-3368 or Marc Thomas at
202-551-3452
with any questions.



FirstName LastNamePaul J. Brody                                 Sincerely,
Comapany NameInteractive Brokers Group, Inc.
                                                                Division of
Corporation Finance
June 20, 2019 Page 2                                            Office of
Financial Services
FirstName LastName