IBAS Ibasis (MM)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14D-9

SOLICITATION/ RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 21)

iBasis, Inc.

(Name of Subject Company)

iBasis, Inc.

(Name of Person Filing Statement)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

450732201

(CUSIP Number of Class of Securities)

Ofer Gneezy
President & Chief Executive Officer
20 Second Avenue, Burlington, MA 01803
(781) 505-7500

(Name, Address and Telephone Number of Persons Authorized to Receive
Notices and Communications on Behalf of Filing Persons)

Copies to:

o     Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

This Amendment No. 21 to the Solicitation/Recommendation Statement on Schedule 14D-9 (as amended and supplemented from time to time, the “Schedule 14D-9”) amends and supplements the Schedule 14D-9, originally filed by iBasis, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “SEC”) on July 30, 2009, relating to the tender offer by KPN B.V., a private limited liability company organized under the laws of The Netherlands (“Purchaser”), which is a wholly owned subsidiary of Koninklijke KPN N.V., a public company incorporated under the laws of The Netherlands (“KPN”), pursuant to which Purchaser has offered to buy all outstanding Shares that it does not already own, upon the terms and subject to the conditions set forth in the offer to purchase dated July 28, 2009 (the “Offer to Purchase”) and the related letter of transmittal (which, together with any amendments or supplements thereto, collectively constitute the “Offer”). The Offer is described in a Tender Offer Statement and Rule 13e-3 Transaction Statement filed by KPN, Purchaser and Celtic ICS Inc. under cover of Schedule TO with the SEC on July 28, 2009, as amended. Capitalized terms used but not defined herein have the meanings ascribed to them in the Schedule 14D-9.

Item 2.    Identity and Background of Filing Person.

Item 2(b) of the Schedule 14D-9 is hereby amended and supplemented by adding the following after the last paragraph thereof:

“On December 9, 2009, Purchaser issued a press release announcing that Purchaser was extending the expiration date of the Amended Offer to 12:00 midnight, New York City time, on Friday, December 18, 2009. On December 9, 2009, Purchaser and KPN also filed Amendment No. 9 to the Schedule TO, which amended and supplemented the Schedule TO in order to reflect, among other things, the extension of the expiration date.”

Item 9.    Exhibits.

Item 9 of the Schedule 14D-9 is hereby amended and supplemented by adding the following exhibit thereto:

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SIGNATURES

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

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