<PAGE>

                                                                 Exhibit 31(a)
                                    TXU CORP.
                       Certificate Pursuant to Section 302
                         of Sarbanes - Oxley Act of 2002
                              CERTIFICATION OF CEO

     I, Erle Nye, Chairman of the Board and Chief Executive of TXU Corp.,
certify that:

1.   I have reviewed this quarterly report on Form 10-Q of TXU
     Corp.;

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

3.   Based on my knowledge, the financial statements, and other
     financial information included in this report, fairly present
     in all material respects the financial condition, results of
     operations and cash flows of the registrant as of, and for,
     the periods presented in this report;

4.   The registrant's other certifying officer(s) and I are
     responsible for establishing and maintaining disclosure
     controls and procedures (as defined in Exchange Act Rules
     13a-15(e) and 15d-15(e)) for the registrant and have:

        a. Designed such disclosure controls and procedures, or caused
           such disclosure controls and procedures to be designed under
           our supervision, to ensure that material information relating
           to the registrant, including its consolidated subsidiaries, is
           made known to us by others within those entities, particularly
           during the period in which this report is being prepared;

        b. Evaluated the effectiveness of the registrant's disclosure
           controls and procedures and presented in this report our
           conclusions about the effectiveness of the disclosure controls
           and procedures, as of the end of the period covered by this
           report based on such evaluation; and

        c. Disclosed in this report any change in the registrant's
           internal control over financial reporting that occurred during
           the registrant's most recent fiscal quarter (the registrant's
           fourth fiscal quarter in the case of an annual report) that
           has materially affected, or is reasonably likely to materially
           affect, the registrant's internal control over financial
           reporting; and

5.   The registrant's other certifying officer(s) and I have disclosed,
     based on our most recent evaluation of internal control over financial
     reporting, to the registrant's auditors and the audit committee of the
     registrant's board of directors (or persons performing the equivalent
     functions):

        a. All significant deficiencies and material weaknesses in the
           design or operation of internal control over financial
           reporting which are reasonably likely to adversely affect the
           registrant's ability to record, process, summarize and report
           financial information; and

        b. Any fraud, whether or not material, that involves management
           or other employees who have a significant role in the
           registrant's internal control over financial reporting.




Date:  November 12, 2003             /s/ Erle Nye
                            -------------------------------------------------
                            Signature:  Erle Nye
                            Title:  Chairman of the Board and Chief Executive