iBasis Provides Update on U.S. Federal Court Ruling on Universal Service Fund Contribution and Other Fees

Effect of Ruling is a Pre-acquisition Contingency, Will Not Result in Charge Against Earnings

BURLINGTON, Mass. - December 6, 2007 - iBasis (NASDAQ: IBAS), the global VoIP company, today provided an update regarding a December 4, 2007 ruling by the U.S. Court of Appeals for the District of Columbia (Court of Appeals) related to contributions to the Federal Universal Service Fund (USF) and the payment of other fees connected with iBasis' Retail prepaid calling services.

On June 30, 2006, the Federal Communications Commission announced a new rule that requires prepaid calling service providers that utilize Internet Protocol to contribute to the Universal Service Fund and pay other regulatory fees. This ruling, which became effective on October 31, 2006, also imposes these fees on a retroactive basis. The Company filed an appeal opposing the retroactive application of this ruling with the Court of Appeals, and oral arguments were held before the Court of Appeals in early October 2007. On December 4, 2007 the Court of Appeals issued an order denying our appeal of the retroactive application of the June 30, 2006 Order.

The Company began accruing and paying for these fees on our Retail revenue prospectively, beginning in the third quarter of 2006. We currently estimate the maximum potential amount of USF and other fees related to our Retail revenue prior to the effective date of the ruling of October 31, 2006, is approximately $3.2 million, of which the Company previously accrued $0.6 million for the period of July 1, 2006 through October 31, 2006. As a result, we currently estimate the maximum potential amount of USF and other fees for the period prior to the third quarter of 2006, which we have not previously accrued or paid, to be approximately $2.6 million.

As these unaccrued fees of approximately $2.6 million for the period prior to the third quarter of 2006 are considered to be a pre-acquisition contingency they will be treated as part of the purchase accounting related to iBasis' transaction with Royal KPN N.V., which was completed on October 1, 2007, resulting in a corresponding increase in goodwill and accrued liabilities as of that date. As such, the accrual for these fees will not impact our results of operations.

About iBasis

Founded in 1996, iBasis (NASDAQ: IBAS) is a leading wholesale carrier of international long distance telephone calls and a provider of retail prepaid calling services and enhanced services for mobile operators. iBasis customers include KPN, KPN Mobile, E-plus, BASE, and many other large telecommunications carriers such as AT&T, Verizon, Vodafone, China Mobile, China Unicom, IDT, Qwest, Skype, Telecom Italia, Telefonica, and Yahoo. In October 2007, iBasis acquired KPN Global Carrier Services to create one of the three largest carriers of international voice traffic in the world (1), and KPN became a majority stockholder of iBasis. On a pro forma basis, the combined company carried more than 20 billion minutes of international voice over IP (VoIP) traffic in 2006. The Company can be reached at its worldwide headquarters in Burlington, Mass., USA at +1 781-505-7500 or on the Internet at www.ibasis.com.