UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934

Filed by the Registrant    [ ]

Filed by a Party other than the Registrant    [X]

Check the appropriate box:
[ ]    Preliminary Proxy Statement
[ ]    Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
[ ]    Definitive Proxy Statement
[ ]    Definitive Additional Materials
[X]    Soliciting Material Pursuant to §240.14a-12


Ceridian Corporation
(Name of Registrant as Specified In Its Charter)

Pershing Square, L.P.
Pershing Square II, L.P.
Pershing Square International, Ltd.
(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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[ ]  Fee paid previously with preliminary materials.
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On July 5, 2007, representatives of Pershing Square Capital Management, L.P., the investment manager to Pershing Square, L.P., Pershing Square II, L.P. and Pershing Square International, Ltd., notified Ceridian Corporation that because a member of the incumbent Board of Ceridian has chosen not to stand for reelection at Ceridian’s upcoming 2007 Annual Meeting and Ceridian has consequently reduced the size of its Board up for election at the 2007 Annual Meeting, the investment funds affiliated with the foregoing Pershing Square entitites did not intend to nominate Professor Michael E. Porter unless Ceridian increased the number of seats to be filled. These funds expect, however, that if their nominees are elected they will increase the board size by one and fill the vacancy created with Professor Porter.

SECURITY HOLDERS ARE ADVISED TO READ THE PROXY STATEMENT AND OTHER DOCUMENTS RELATED TO THE SOLICITATION OF PROXIES BY PERSHING SQUARE, L.P., PERSHING SQUARE II, L.P., PERSHING SQUARE INTERNATIONAL, LTD. AND CERTAIN OF THEIR RESPECTIVE AFFILIATES FROM THE STOCKHOLDERS OF CERIDIAN CORPORATION FOR USE AT ITS ANNUAL MEETING WHEN AND IF THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION, INCLUDING INFORMATION RELATING TO THE PARTICIPANTS IN ANY SUCH PROXY SOLICITATION. WHEN AND IF COMPLETED, A DEFINITIVE PROXY STATEMENT AND A FORM OF PROXY WILL BE MAILED TO THE STOCKHOLDERS OF CERIDIAN CORPORATION AND WILL BE AVAILABLE AT NO CHARGE AT THE SECURITIES AND EXCHANGE COMMISSION’S WEBSITE AT HTTP://WWW.SEC.GOV. Information rELATING TO THE POTENTIAL PARTICIPANTS in THE POTENTIAL proxy solicitation from the sTOCKholders of ceridian corporation is available in the Additional definitive proxy soliciting materials CONCERNING CERIDIAN CORPORATION filed with the SEcurities and exchange commission BY PERSHING SQUARE, L.P., PERSHING SQUARE II, L.P. AND PERSHING SQUARE INTERNATIONAL, LTD. on january 23, 2007 (FILE/FILM NO: 001-15168/07544605).