EXHIBIT 31
CERTIFICATION OF CHIEF EXECUTIVE OFFICER
I, John W. Hall, certify that:
1. I have reviewed this quarterly report on Form 10-Q of Onyx AcceptanceCorporation;
2. Based on my knowledge, this report does not contain any untrue statementof a material fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which such statementswere made, not misleading with respect to the period covered by thisreport;
3. Based on my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all materialrespects the financial condition, results of operations and cash flows ofthe registrant as of, and for, the periods presented in this report;
4. The registrant’s other certifying officer and I are responsible forestablishing and maintaining disclosure controls and procedures (asdefined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrantand have:
 a) designed such disclosure controls and procedures, or causedsuch disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made knownto us by others within those entities, particularly during theperiod in which this report is being prepared;  b) evaluated the effectiveness of the registrant’s disclosurecontrols and procedures and presented in this report our conclusionsabout the effectiveness of the disclosure controls and procedures,as of the end of the period covered by this report based on suchevaluation; and  c) disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during theregistrant’s most recent fiscal quarter that has materiallyaffected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting; and
5. The registrant’s other certifying officer and I have disclosed, based onour most recent evaluation of internal control over financial reporting,to the registrant’s auditors and the audit committee of the registrant’sboard of directors (or persons performing the equivalent functions):
 a) all significant deficiencies and material weaknesses in thedesign or operation of internal control over financial reportingwhich are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financialinformation; and  b) any fraud, whether or not material, that involves managementor other employees who have a significant role in the registrant’sinternal control over financial reporting.
Date: November 12, 2004 /s/ JOHN W. HALLJohn W. HallPresident, CEO and Principal Executive Officer
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EXHIBIT 31
CERTIFICATION OF CHIEF FINANCIAL OFFICER
I, Don P. Duffy, certify that:
1. I have reviewed this quarterly report on Form 10-Q of Onyx AcceptanceCorporation;
2. Based on my knowledge, this report does not contain any untrue statementof a material fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which such statementswere made, not misleading with respect to the period covered by thisreport;
3. Based on my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all materialrespects the financial condition, results of operations and cash flows ofthe registrant as of, and for, the periods presented in this report;
4. The registrant’s other certifying officer and I are responsible forestablishing and maintaining disclosure controls and procedures (asdefined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrantand have:
 a) designed such disclosure controls and procedures, or causedsuch disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made knownto us by others within those entities, particularly during theperiod in which this report is being prepared;  b) the effectiveness of the registrant’s disclosure controls andprocedures and presented in this report our conclusions about theeffectiveness of the disclosure controls and procedures, as of theend of the period covered by this report based on such evaluation;and  c) disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during theregistrant’s most recent fiscal quarter that has materiallyaffected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting; and
5. The registrant’s other certifying officer and I have disclosed, based onour most recent evaluation of internal control over financial reporting,to the registrant’s auditors and the audit committee of the registrant’sboard of directors (or persons performing the equivalent functions):
 a) all significant deficiencies and material weaknesses in thedesign or operation of internal control over financial reportingwhich are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financialinformation; and  b) any fraud, whether or not material, that involves managementor other employees who have a significant role in the registrant’sinternal control over financial reporting.
Date: November 12, 2004 /s/ DON P. DUFFYDon P. Duffy Executive Vice President,CFO and Principal Financial Officer
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