80 The impact of the carbon price on the consolidated entity’s future  cash flows has been included in the estimation of the recoverable  amount of the consolidated entity’s cash-generating units when  testing for impairment at 30 June 2012. The introduction of the  carbon price does not impact on the consolidated entity’s operating  results for the year ended 30 June 2012. During the year ended 30 June 2012 AGL completed Project  Spectrum. Project Spectrum transferred AGL’s business customers  onto the same SAP billing platform as its consumer customers  (excluding 118,600 Powerdirect customers). This single SAP billing  platform has materially enhanced the granularity of analysis that is  able to be performed on customer balances. Using this enhanced  capability, AGL undertook a comprehensive review of debtors,  unbilled sales, creditors and unbilled distribution costs. This review highlighted that, in prior periods, AGL had consistently  but incorrectly estimated period-end distribution liabilities by using  a methodology to accrue distribution charges based on an  estimated number of days not yet billed by the relevant distributor  in each state. AGL believed that this estimate fully accounted for  invoices relating to the relevant period end that had yet to be  received. However, this estimate has never fully accounted for  invoices received after the relevant period end relating to  distribution charges incurred prior to the period end. It has been impracticable to allocate the increased liability between  opening balance liabilities arising from business acquisitions and  increased expenses in prior periods. Accordingly, opening retained  earnings for the year ended 30 June 2012 has been reduced by  $79.9 million as a result of an increase in the opening distribution  liability of $114.1 million and a net decrease in tax liabilities of  $34.2 million. Actual distribution expense for the year ended  30 June 2012 has been correctly reflected in current year  operating profit. The consolidated entity reports segment information on the same  basis as the internal management reporting structure, which drives  how the consolidated entity is organised and managed.  The consolidated entity has identified its operating segments based  on the internal reports that are regularly reviewed and used by the  Board of Directors (the chief operating decision maker) in assessing  performance and in determining the allocation of resources.  Management has determined the operating segments based on the  manner in which products are sold, whether retail or wholesale, and  the nature of the services provided.  From 1 July 2011, the following changes were made to the  consolidated entity’s operating segments:  Segment results are reported according to the internal  management reporting structure at the reporting date. Segment  comparative information has been restated to reflect the changes  described above.  On 22 June 2012, Great Energy Alliance Corporation Pty Limited  (GEAC), the owner of the Loy Yang A power station, received a  coal-fired generation assistance cash payment of $240.1 million  from the Australian Government as part of this arrangement.  GEAC, a subsidiary of AGL Energy Limited, also anticipates receiving  allocations of approximately 10 million free carbon permits on  1 September 2013, 2014, 2015 and 2016, respectively that are  conditional on Loy Yang A satisfying a power system reliability  test and publishing a Clean Energy Investment Plan. To assist the electricity generation sector transition to lower  carbon emissions and to maintain secure energy supplies, the  Government established an Energy Security Fund. Under the  Energy Security Fund, the Government is providing a total of  $5.5 billion in the form of cash and free carbon permits to highly  emissions-intensive coal-fired generators, over six years. Cash  payments of $1 billion were made in June 2012 and eligible  generators will share in four annual allocations of 41.7 million  free carbon permits to the value of $4.5 billion, commencing  on 1 September 2013. The carbon pricing mechanism has a two phased approach: a fixed  price mechanism, followed by an emission trading scheme (ETS).  Under the carbon pricing scheme, as of 1 July 2012, every tonne of  carbon dioxide equivalent (CO$_{2}$-e) produced by approximately 500  of Australia’s largest emitters will be priced at $23 per tonne. For  the first three years, the carbon price is fixed, rising annually by  2.5%. On 1 July 2015, the pricing mechanism will transition to  the floating ETS. On 8 November 2011, the Federal Parliament passed the Clean  Energy Legislative Package, which introduced a carbon price into  the Australian economy from 1 July 2012 to reduce carbon  pollution and move to a clean energy future.  The consolidated entity measures the cost of equity-settled  transactions with employees by reference to the fair value of the  equity instruments at the date at which they are granted. The fair  value is determined by an external valuer using the Black-Scholes  and Monte Carlo simulation methods, with the assumptions  detailed in Note 49. The accounting estimates and assumptions  relating to equity-settled share-based payments would have no  impact on the carrying amounts of assets and liabilities within the  next annual reporting period but may impact expenses and equity. Various actuarial assumptions are utilised in the determination  of the consolidated entity’s defined benefit obligations. These  assumptions and the related carrying amounts are discussed  in Note 48. The consolidated entity estimates the future removal and  restoration costs of electricity generation assets, oil and gas  production facilities, wells, pipelines and related assets at the time  of installation of the assets. In most instances, removal of these  assets will occur many years into the future. The calculation of this  provision requires management to make assumptions regarding the  removal date, application of environmental legislation, the extent  of restoration activities required and available technologies. The  carrying amount of the provision for environmental restoration is  disclosed in Note 31. Note 2 – Significant accounting judgements, estimates  and assumptions (continued) Provision for environmental restoration Note 3 – Correction of unbilled distribution liability Defined benefit superannuation plans Share-based payment transactions Carbon price Note 4 – Segment information Operating segments > Business customers (formerly commercial and industrial)  previously reported in the Retail Energy operating segment are  now included in the Merchant Energy operating segment; and > Certain administration costs (mainly finance and information  technology) previously reported in the Retail Energy, Merchant  Energy and Upstream Gas operating segments are now included  in Other.  Consolidated  Notes to the  Financial  Statements