SECTION 409A POLICIES AND PROCEDURES
THESE POLICIES AND PROCEDURES apply to and amend all plans, agreements and arrangements by
and between iBasis, Inc. (the “ Corporation ”) and any employee that are or could be subject to Section 409A of
the Internal Revenue Code of 1986, as amended (the “ Code ”), which have not previously been amended to
comply with Section 409A in a manner that conflicts with the provisions herein (collectively, the “ Agreements ”).
These policies and procedures are made by the undersigned pursuant to authority delegated by the
Compensation Committee of the Board of Directors of the Corporation, effective as of December 31, 2008.
1. Specified Employees . All employees who are identified by the Corporation as officers under
Section 16 of the Securities Exchange Act of 1934 or as corporate officers, including all employees who
are at the level of vice president and above, at any time during the twelve-month period ending on
December 31st of any year (the “ Identification Date ”) shall be treated for the twelve-month period
beginning on the Identification Date as “Specified Employees,” as that term is used in Section 409A, for
purposes of all Agreements.
2. Six-Month Delay . Notwithstanding any other provision in any Agreement, if an employee is a
Specified Employee at the time of his or her separation from service, no amount that is subject to
Section 409A and that becomes payable by reason of such separation from service shall be paid to such
employee before the earlier of (i) the expiration of the six-month period measured from the date of such
employee’s separation from service, and (ii) the date of such employee’s death. The required delay in
payment shall be met by accumulating payments to which a Specified Employee would otherwise be
entitled during the first six months following the date of separation from service an