**Exhibit 31.2**

**CERTIFICATION PURSUANT SECTION 302 OFTHE SARBANES-OXLEY ACT OF 2002**

I, Richard Tennant,certify that:

1.                 I have reviewedthis annual report of Form 10-K of iBasis, Inc.;

2.                 Based on myknowledge, this annual report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this annual report;

3.                 Based on myknowledge, the financial statements, and other financial information includedin this annual report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this annual report;

4.                 The registrant’sother certifying officers and I are responsible for establishing andmaintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e) and internal control over financial reporting (as definedin Exchange Act Rules 13a-15(f) and 15d-15(f)) for theregistrant and we have:

a)               Designed suchdisclosure controls and procedures, or caused such control procedures to bedesigned under our supervision, to ensure that material information relating tothe registrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisannual report is being prepared;

b)              Designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles.

c)               Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thereport based on such evaluation; and

d)              Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, the registrantsinternal control over financial reporting; and

5.                 The registrant’sother certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the registrant’sauditors and the audit committee of registrant’s board of directors (or personsperforming the equivalent functions):

a)               All significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonably likely to adversely affectthe registrant’s ability to record, process, summarize and report financialinformation; and

b)              Anyfraud, whether or not material, that involves management or other employees whohave a significant role in the registrant’s internal control over financialreporting.

| Date: March 15, 2006 |                          |
|---------------------------|-------------------------------|
|                      | /s/ RICHARD  TENNANT          |
|                      | Richard Tennant               |
|                      | Chief Financial Officer       |
|                      | (Principal Financial Officer) |

 

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