UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ------------- SCHEDULE 13D UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. 1)* TransAlta Corporation -------------------------------------------------------------------------------- (Name of Issuer) Common Stock -------------------------------------------------------------------------------- (Title of Class of Securities) 89346D107 -------------------------------------------------------------------------------- (CUSIP Number) Mr. Christopher Hohn The Children's Investment Fund Management (UK) LLP 7 Clifford Street London W1S 2WE United Kingdom +44 20 7440 2330 With a copy to: Marc Weingarten, Esq. Schulte Roth & Zabel LLP 919 Third Avenue New York, New York 10022 (212) 756-2000 -------------------------------------------------------------------------------- (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) (Continued on following pages) September 8, 2008 -------------------------------------------------------------------------------- (Date of Event which Requires Filing of This Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box. [ ] NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to be sent. -------------------------- * The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). (Page 1 of 8 Pages) -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 2 OF 8 Pages -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) The Children's Investment Fund Management (UK) LLP -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS* AF -------------------------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [X] -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION England -------------------------------------------------------------------------------- 7 SOLE VOTING POWER -0- -------------------------------------------------------------------------------- NUMBER OF 8 SHARED VOTING POWER SHARES BENEFICIALLY 14,117,400 OWNED BY ---------------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER REPORTING PERSON WITH -0- ---------------------------------------------------------- 10 SHARED DISPOSITIVE POWER 14,117,400 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 7.1% -------------------------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 7.1% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 3 OF 8 Pages -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) The Children's Investment Fund Management (Cayman) Ltd. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS* AF -------------------------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [X] -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands -------------------------------------------------------------------------------- 7 SOLE VOTING POWER -0- -------------------------------------------------------------------------------- NUMBER OF 8 SHARED VOTING POWER SHARES BENEFICIALLY 14,117,400 OWNED BY ---------------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER REPORTING PERSON WITH -0- ---------------------------------------------------------- 10 SHARED DISPOSITIVE POWER 14,117,400 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 7.1% -------------------------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 7.1% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON* CO -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 4 OF 8 Pages -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) The Children's Investment Master Fund -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS* WC -------------------------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [X] -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands -------------------------------------------------------------------------------- 7 SOLE VOTING POWER -0- -------------------------------------------------------------------------------- NUMBER OF 8 SHARED VOTING POWER SHARES BENEFICIALLY 14,117,400 OWNED BY ---------------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER REPORTING PERSON WITH -0- ---------------------------------------------------------- 10 SHARED DISPOSITIVE POWER 14,117,400 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 7.1% -------------------------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 7.1% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON* CO -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 5 OF 8 Pages -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Christopher Hohn -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS* AF -------------------------------------------------------------------------------- 5 CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [X] -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION United Kingdom -------------------------------------------------------------------------------- 7 SOLE VOTING POWER -0- -------------------------------------------------------------------------------- NUMBER OF 8 SHARED VOTING POWER SHARES BENEFICIALLY 14,117,400 OWNED BY ---------------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER REPORTING PERSON WITH -0- ---------------------------------------------------------- 10 SHARED DISPOSITIVE POWER 14,117,400 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 7.1% -------------------------------------------------------------------------------- 12 CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 7.1% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON* IN -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 6 OF 8 Pages -------------------------------------------------------------------------------- The Schedule 13D filed on August 15, 2008 (the "Schedule 13D") by The Children's Investment Fund Management (UK) LLP, an English limited liability partnership, The Children's Investment Fund Management (Cayman) Ltd., a Cayman Islands exempted company, The Children's Investment Master Fund, a Cayman Islands exempted company, and Christopher Hohn (together, the "Reporting Persons") relating to the shares ("Shares") of common stock of TransAlta Corporation (the "Issuer"), is hereby amended as set forth below by this Amendment No. 1 to the Schedule 13D. ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION Item 3 of the Schedule 13D is hereby amended and restated as follows: A total of approximately $439,399,739.99, including commissions (using an exchange rate of US $1.00 = Cdn $1.0698, the exchange rate in effect on September 8, 2008, according to Bloomberg), was paid to acquire the Shares reported herein. The source of funds used to acquire such Shares was the general working capital of the TCI Fund. ITEM 5. INTEREST IN SECURITIES OF THE ISSUER Paragraphs (a), (b), and (c) of Item 5 of the Schedule 13D are hereby amended and restated as follows: (a) As of the close of business on September 8, 2008, the Reporting Persons beneficially owned an aggregate of 14,117,400 Shares, constituting approximately 7.1% of the Shares outstanding. The aggregate percentage of Shares beneficially owned by the Reporting Persons is based upon 197,600,000 Shares outstanding, which is the total number of Shares issued and outstanding as of June 30, 2008 as reported in the Issuer's Form 6-K filed on August 4, 2008. (b) Each of the Reporting Persons share power to vote and direct the disposition of the Shares held by the TCI Fund. (c) Information concerning transactions in the Shares effected by the Reporting Persons during the past sixty days is set forth in Appendix A hereto and is incorporated herein by reference. -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 7 OF 8 Pages -------------------------------------------------------------------------------- SIGNATURES After reasonable 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. Dated: September 10, 2008 THE CHILDREN'S INVESTMENT FUND MANAGEMENT (UK) LLP /s/ Christopher Hohn ------------------------------ Christopher Hohn Managing Partner THE CHILDREN'S INVESTMENT FUND MANAGEMENT (CAYMAN) LTD. /s/ David DeRosa ------------------------------ David DeRosa Director THE CHILDREN'S INVESTMENT MASTER FUND /s/ David DeRosa ------------------------------ David DeRosa Director /s/ Christopher Hohn ------------------------------ Christopher Hohn -------------------------------------------------------------------------------- CUSIP NO. 89346D107 SCHEDULE 13D PAGE 8 OF 8 Pages -------------------------------------------------------------------------------- APPENDIX A TRANSACTIONS IN THE SHARES EFFECTED BY THE REPORTING PERSONS SINCE THE FILING OF THE SCHEDULE 13D (UNLESS OTHERWISE STATED, ALL TRANSACTIONS WERE EFFECTED IN THE OPEN MARKET) The Children's Investment Master Fund Date of Trade Shares Purchased (Sold) Price per Share(1) 15-Aug-08 342,300 33.216 18-Aug-08 12,900 33.824 20-Aug-08 14,300 33.835 21-Aug-08 200 34.450 02-Sep-08 175,200 33.477 03-Sep-08 1,123,800 33.479 05-Sep-08 200,000 31.513 08-Sep-08 158,200 31.962 ---------------- (1) US dollar amounts calculated using exchange rates in effect on the date of trade.