CHANGE IN CONTROL SEVERANCE AGREEMENT

Exhibit 10.10

CHANGE IN CONTROL SEVERANCE AGREEMENT

        THIS AGREEMENT, effective as of August 1, 2007, is made by and between CF Industries Holdings, Inc., a Delaware corporation (the "Company"), and Wendy Jablow Spertus (the "Executive").

        WHEREAS, the Company considers it essential to the best interests of its stockholders to foster the continued employment of key management personnel; and

        WHEREAS, the Board recognizes that the possibility of a Change in Control exists and that such possibility, and the uncertainty and questions which it may raise among management, may result in the departure or distraction of management personnel to the detriment of the Company and its stockholders; and

        WHEREAS, the Board has determined that appropriate steps should be taken to reinforce and encourage the continued attention and dedication of members of the Company's management, including the Executive, to their assigned duties without distraction in the face of potentially disturbing circumstances arising from the possibility of a Change in Control;

        NOW, THEREFORE, in consideration of the premises and the mutual covenants herein contained, the Company and the Executive hereby agree as follows:

        1.     Defined Terms.     The definitions of capitalized terms used in this Agreement are provided in the last Section hereof.

        2.     Term of Agreement.     The Term of this Agreement shall continue through December 31, 2008; provided , however , that commencing on January 1, 2008 and each January 1 thereafter, the Term shall automatically be extended for one additional year unless, not later than September 30 of the preceding year, the Company or the Executive shall have given notice not to extend the Term; and further provided , however , that if a Change in Control shall have occurred during the Term, the Term shall expire no earlier than twenty-four (24) months beyond the month in which such Change in Control occurred.

        3.     Company's Covenants Summarized.     In order to induce the Executive to remain in the employ of the Company and in consideration of the Executive's covenants set forth in Section 4 hereof, the Company agrees, under the conditions described herein, to pay the Executive the Severance Payments and the other payments and benefits described herein. Except as provided in Section 9.1 hereof, no Severance Payments shall be payable under this Agreement unless there shall have been (or, under the terms of the second sentence of Section 6.1 hereof, there shall be deemed to have been) a termination of the Executive's employment with the Company following a Change in Control and during the Term. This Agreement shall not be construed as creating an express or implied contract of employment and, except as otherwise agreed in writing between the Executive and the Company, the Executive shall not have any right to be retained in the employ of the Company.

        4.     The Executive's Covenants.     The Executive agrees that, subject to the terms and conditions of this Agreement, in the event of a Potential Change in Control during the Term, the Executive will remain in the employ of the Company until the earliest of (i) a date which is six (6) months from the date of such Potential Change in Control, (ii) the date of a Change in Control, (iii) the date of termination by the Executive of the Executive's employment for Good Reason or by reason of death, Disability or Retirement, or (iv) the termination by the Company of the Executive's employment for any reason.

        5.     Compensation Other Than Severance Payments.     

        5.1   Following a Change in Control and during the Term, during any period that the Executive fails to perform the Executive's full-time duties with the Company as a result of incapacity due to physical or mental illness, the Company shall pay the Executive's full salary to the Executive at the rate in effect at the commencement of any such period, together with all compensation and benefits payable to the Executive under the terms of any compensation or benefit plan, program or arrangement

maintained by the Company during such period (other than any disability plan), until the Executive's employment is terminated by the Company for Disability.

        5.2   If the Executive's employment shall be terminated for any reason following a Change in Control and during the Term, the Company shall pay the Executive's full salary to the Executive through the Date of Termination at the rate in effect immediately prior to the Date of Termination or, if higher, the rate in effect immediately prior to the first occurrence of an event or circumstance constituting Good Reason, together with all compensation and benefits payable to the Executive through the Date of Termination under the terms of the Company's compensation and benefit plans, programs or arrangements as in effect immediately prior to the Date of Termination or, if more favorable to the Executive, as in effect immediately prior to the first occurrence of an event or circumstance constituting Good Reason.

        5.3   If the Executive's employment shall be terminated for any reason following a Change in Control and during the Term, the Company shall pay to the Executive the Executive's normal post-termination compensation and benefits as such payments become due. Such post-termination compensation and benefits shall be determined under, and paid in accordance with, the Company's retirement, insurance and other compensation or benefit plans, programs and arrangements as in effect immediately prior to the Date of Termination or, if more favorable to the Executive, as in effect immediately prior to the occurrence of the first event or circumstance constituting Good Reason.

        6.     Severance Payments.     

        6.1   Subject to Section 6.2 hereof, if the Executive's employment is terminated following a Change in Control and during the Term, other than (A) by the Company for Cause, (B) by reason of death or Disability, or (C) by the Executive without Good Reason, then the Company shall pay the Executive the amounts, and provide the Executive the benefits, described in this Section 6.1 ("Severance Payments"), in addition to any payments and benefits to which the Executive is entitled under Section 5 hereof. For purposes of this Agreement, the Executive's employment shall be deemed to have been terminated following a Change in Control by the Company without Cause or by the Executive with Good Reason, if (i) the Executive's employment is terminated by the Company without Cause prior to a Change in Control (whether or not a Change in Control ever occurs) and such termination was at the request or direction of a Person who has entered into an agreement with the Company the consummation of which would constitute a Change in Control, (ii) the Executive terminates his or her employment for Good Reason prior to a Change in Control (whether or not a Change in Control ever occurs) and the circumstance or event which constitutes Good Reason occurs at the request or direction of such Person, or (iii) the Executive's employment is terminated by the Company without Cause or by the Executive for Good Reason and such termination or the circumstance or event which constitutes Good Reason is otherwise in connection with or in anticipation of a Change in Control (whether or not a Change in Control ever occurs).

•         (A)  In lieu of any further salary payments to the Executive for periods subsequent to the Date of Termination and in lieu of any severance benefit otherwise payable to the Executive, the Company shall pay to the Executive a lump sum severance payment, in cash, equal to one times the sum of (i) the Executive's base salary as in effect immediately prior to the Date of Termination or, if higher, in effect immediately prior to the first occurrence of an event or circumstance constituting Good Reason, and (ii) the Executive's target annual bonus pursuant to any annual bonus or incentive plan maintained by the Company in respect of the fiscal year in which the Date of Termination occurs or, if higher, the fiscal year in which the first event or circumstance constituting Good Reason occurs.

          (B)  For the twelve month period immediately following the Date of Termination, the Company shall arrange to provide the Executive and his or her dependents life, disability, accident and health insurance benefits substantially similar to those provided to the Executive and his or

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  her dependents immediately prior to the Date of Termination or, if more favorable to the Executive, those provided to the Executive and his or her dependents immediately prior to the first occurrence of an event or circumstance constituting Good Reason, at no greater after tax cost to the Executive than the after tax cost to the Executive immediately prior to such date or occurrence; provided , however , that, unless the Executive consents to a different method, such health insurance benefits shall be provided through a third-party insurer. Benefits otherwise receivable by the Executive pursuant to this Section 6.1(B) shall be reduced to the extent benefits of the same type are received by or made available to the Executive during the twelve month period following the Executive's termination of employment (and any such benefits received by or made available to the Executive shall be reported to the Company by the Executive); provided , however , that the Company shall reimburse the Executive for the excess, if any, of the after tax cost of such benefits to the Executive over such cost immediately prior to the Date of Termination or, if more favorable to the Executive, the first occurrence of an event or circumstance constituting Good Reason. If the Severance Payments shall be decreased pursuant to Section 6.2 hereof, and the Section 6.1(B) benefits which remain payable after the application of Section 6.2 hereof are thereafter reduced pursuant to the immediately preceding sentence, the Company shall, no later than five (5) business days following such reduction, pay to the Executive the least of (a) the amount of the decrease made in the Severance Payments pursuant to Section 6.2 hereof, (b) the amount of the subsequent reduction in these Section 6.1(B) benefits, or (c) the maximum amount which can be paid to the Executive without being, or causing any other payment to be, nondeductible by reason of section 280G of the Code.

          (C)  In addition to the benefits to which the Executive is entitled under each DC Pension Plan, the Company shall pay the Executive a lump sum amount, in cash, equal to the sum of (1) the amount that would have been contributed or allocated to each DC Pension Plan by the Company on the Executive's behalf (without regard to whether such amount would be vested) during the year immediately following the Date of Termination, determined (x) as if the Executive made the maximum permissible contributions thereto during such period, (y) as if the Executive earned compensation during such period at a rate equal to the Executive's compensation (as defined in the DC Pension Plans) during the twelve (12) months immediately preceding the Date of Termination or, if higher, during the twelve months immediately prior to the first occurrence of an event or circumstance constituting Good Reason, and (z) without regard to any amendment to the DC Pension Plans made subsequent to a Change in Control and on or prior to the Date of Termination, which amendment adversely affects in any manner the computation of benefits thereunder and (2) all other amounts credited to the Executive's account under each DC Pension Plan to the extent such amounts were unvested on the Date of Termination.

          (D)  If the Executive would have become entitled to benefits under the Company's post-retirement health care or life insurance plans, as in effect immediately prior to the Date of Termination or, if more favorable to the Executive, as in effect immediately prior to the first occurrence of an event or circumstance constituting Good Reason, had the Executive's employment terminated at any time during the period of twelve months after the Date of Termination, the Company shall provide such post-retirement health care or life insurance benefits to the Executive and the Executive's dependents commencing on the later of (i) the date on which such coverage would have first become available and (ii) the date on which benefits described in subsection (B) of this Section 6.1 terminate. If the operation of this Section 6.1(D) would result in adverse tax consequences to the Executive as a result of the Executive's participation in the Company's post-retirement health care or life insurance plans, the Company shall instead provide substantially similar benefits and coverage through a third party insurer.

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          (E)  The Company shall provide the Executive with outplacement services suitable to the Executive's position for a period of one year or, if earlier, until the first acceptance by the Executive of an offer of employment.

          (F)  Notwithstanding any provision of any annual or long-term incentive plan to the contrary, the Company shall pay to the Executive a lump sum amount, in cash, equal to the sum of (i) any unpaid incentive compensation which has been allocated or awarded to the Executive for a completed fiscal year or other measuring period preceding the Date of Termination under any such plan and which, as of the Date of Termination, is contingent only upon the continued employment of the Executive to a subsequent date, and (ii) a pro rata portion to the Date of Termination of the aggregate value of all contingent incentive compensation awards to the Executive for all then uncompleted periods under any such plan, calculated as to each such award by multiplying the award that the Executive would have earned on the last day of the performance award period, assuming the achievement, at the target level (or, if greater, based on actual results to Date of Termination), of the individual and corporate performance goals established with respect to such award, by the fraction obtained by dividing the number of full months and any fractional portion of a month during such performance award period through the Date of Termination by the total number of months contained in such performance award period.

        6.2   (A) Notwithstanding any other provisions of this Agreement, in the event that any payment or benefit received or to be received by the Executive (including any payment or benefit received in connection with a Change in Control or the termination of the Executive's employment, whether pursuant to the terms of this Agreement or any other plan, arrangement or agreement) (all such payments and benefits, including the Severance Payments, being hereinafter referred to as the "Total Payments") would not be deductible (in whole or part), by the Company, an affiliate or Person making such payment or providing such benefit as a result of section 280G of the Code, then, to the extent necessary to make such portion of the Total Payments deductible (and after taking into account any reduction in the Total Payments provided by reason of section 280G of the Code in such other plan, arrangement or agreement), the cash Severance Payments shall first be reduced (if necessary, to zero), and all other Severance Payments shall thereafter be reduced (if necessary, to zero); provided , however , that the Executive may elect to have the noncash Severance Payments reduced (or eliminated) prior to any reduction of the cash Severance Payments.

        (B)  For purposes of this limitation, (i) no portion of the Total Payments the receipt or enjoyment of which the Executive shall have waived at such time and in such manner as not to constitute a "payment" within the meaning of section 280G(b) of the Code shall be taken into account, (ii) no portion of the Total Payments shall be taken into account which, in the opinion of tax counsel ("Tax Counsel") reasonably acceptable to the Executive and selected by the accounting firm which was, immediately prior to the Change in Control, the Company's independent auditor (the "Auditor"), does not constitute a "parachute payment" within the meaning of section 280G(b)(2) of the Code, including by reason of section 280G(b)(4)(A) of the Code, (iii) the Severance Payments shall be reduced only to the extent necessary so that the Total Payments (other than those referred to in clauses (i) or (ii)) in their entirety constitute reasonable compensation for services actually rendered within the meaning of section 280G(b)(4)(B) of the Code or are otherwise not subject to disallowance as deductions by reason of section 280G of the Code, in the opinion of Tax Counsel, and (iv) the value of any noncash benefit or any deferred payment or benefit included in the Total Payments shall be determined by the Auditor in accordance with the principles of sections 280G(d)(3) and (4) of the Code.

        (C)  If it is established pursuant to a final determination of a court or an Internal Revenue Service proceeding that, notwithstanding the good faith of the Executive and the Company in applying the terms of this Section 6.2, the Total Payments paid to or for the Executive's benefit are in an amount that would result in any portion of such Total Payments being subject to the Excise Tax, then, if such repayment would result in (i) no portion of the remaining Total Payments being subject to the Excise

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Tax and (ii) a dollar-for-dollar reduction in the Executive's taxable income and wages for purposes of federal, state and local income and employment taxes, the Executive shall have an obligation to pay the Company upon demand an amount equal to the sum of (i) the excess of the Total Payments paid to or for the Executive's benefit over the Total Payments that could have been paid to or for the Executive's benefit without any portion of such Total Payments being subject to the Excise Tax; and (ii) interest on the amount set forth in clause (i) of this sentence at the rate provided in section 1274(b)(2)(B) of the Code from the date of the Executive's receipt of such excess until the date of such payment.

        6.3   The payments provided in subsections (A), (C) and (F) of Section 6.1 hereof shall be made not later than the fifth day following the date upon which the revocation period for the release described in Section 6.6 expires; provided , however , that if the amounts of such payments, and the limitation on such payments set forth in Section 6.2 hereof, cannot be finally determined on or before such day, the Company shall pay to the Executive on such day an estimate, as determined in good faith by the Company, of the minimum amount of such payments to which the Executive is clearly entitled and shall pay the remainder of such payments (together with interest on the unpaid remainder (or on all such payments to the extent the Company fails to make such payments when due) at 120% of the rate provided in section 1274(b)(2)(B) of the Code) as soon as the amount thereof can be determined but in no event later than the thirtieth (30th) day after the Date of Termination. In the event that the amount of the estimated payments exceeds the amount subsequently determined to have been due, such excess shall constitute a loan by the Company to the Executive, payable on the fifth (5th) business day after demand by the Company (together with interest at 120% of the rate provided in section 1274(b)(2)(B) of the Code). At the time that payments are made under this Agreement, the Company shall provide the Executive with a written statement setting forth the manner in which such payments were calculated and the basis for such calculations including, without limitation, any opinions or other advice the Company has received from Tax Counsel, the Auditor or other advisors or consultants (and any such opinions or advice which are in writing shall be attached to the statement). In the event necessary to comply with the provisions of Section 409A of the Code and the guidance issued thereunder, (a) reimbursements to Executive as a result of the operation of Section 6.1(B) hereof shall be made not later than the end of the calendar year following the year in which the reimbursable expense is incurred and (b) if Executive is a "specified employee" (within the meaning of Section 409A(a)(2)(B)(i) of the Code), any reimbursements to Executive as a result of the operation of 6.1(B) hereof with respect to a reimbursable event within the first six months following the Date of Termination shall be made as soon as practicable following the date which is six months and one day following the Date of Termination (subject to clause (a) of this sentence).

        6.4   The Company also shall pay to the Executive all legal fees and expenses incurred by the Executive in disputing in good faith any issue hereunder relating to the termination of the Executive's employment, in seeking in good faith to obtain or enforce any benefit or right provided by this Agreement or in connection with any tax audit or proceeding to the extent attributable to the application of section 4999 of the Code to any payment or benefit provided hereunder. Such payments shall be made within five (5) business days after delivery of the Executive's written requests for payment accompanied with such evidence of fees and expenses incurred as the Company reasonably may require. The Executive's reimbursement rights described in this Section 6.4 shall remain in effect for the Executive's lifetime, provided, that, in order for the Executive to be entitled to reimbursement hereunder, the Executive must submit the written reimbursement request described above within 180 days following the date upon which the applicable expense is incurred.

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