87 AGL Energy Limited Annual Report 2012 2012  $m 2011  $m Deferred tax balances Deferred tax assets/(liabilities) arise from the following: Unbilled revenue (254.2) (208.4) Allowance for doubtful debts 22.6  19.4  Other receivables (0.3) (9.8) Jointly controlled entities 8.3  (7.2) Exploration and evaluation assets (158.4) (154.2) Oil and gas assets (16.3) (34.2) Property, plant and equipment (301.9) (109.2) Intangible assets (10.1) –  Defined benefit superannuation plans 67.1  12.2  Payables and accruals 5.2  40.7  Borrowings (3.0) –  Provisions 107.0  71.0  Derivative financial instruments 10.8  57.0  Deferred revenue 74.7  6.5  Share issue transaction costs 5.2  –  Tax losses 654.8  11.5  Other (2.8) 2.0  Net deferred tax assets/(liabilities) relating to income tax 208.7  (302.7) Deferred tax assets relating to resource rent tax 53.4  –  Net deferred tax assets/(liabilities)  262.1  (302.7) Recognised in the statement of financial position as follows: Deferred tax assets 611.1  –  Deferred tax liabilities  (349.0) (302.7) Net deferred tax assets/(liabilities)  262.1  (302.7) Unrecognised deferred tax assets Deductible temporary differences –  55.0  Tax consolidation Revenue authority matters Extension of Petroleum Resource Rent Tax to onshore projects The Parent Entity and its wholly-owned Australian resident subsidiaries formed a tax-consolidated group under Australian taxation law  with effect from 25 October 2006 and are therefore taxed as a single entity from that date. AGL Energy Limited is the head entity in the  tax-consolidated group.  The members of the tax-consolidated group have entered into a tax sharing and tax funding agreement. The tax funding agreement  requires payments to/from the head entity equal to the current tax liability (asset) assumed by the head entity and any tax-loss deferred  tax asset assumed by the head entity. The payments are recorded as intercompany receivables/payables.  On 29 June 2012, AGL Generation Proprietary Limited, a subsidiary of AGL Energy Limited (AGL), acquired the remaining 67.46% of the  shares in, and loan notes issued by, Great Energy Alliance Corporation Pty Limited (GEAC) and 100% of the shares in Loy Yang Marketing  Holdings Pty Limited (LYMH) which it did not already own. GEAC, LYMH and their subsidiaries are not eligible to be members of the  existing AGL tax-consolidated group. On 23 July 2012, the LYMH entities joined a new tax-consolidated group which was formed by  AGL Generation Holdco Pty Ltd, a subsidiary of AGL. On 27 July 2012, the GEAC entities joined the new tax-consolidated group.  AGL Generation Holdco Pty Ltd is the head entity in the new tax-consolidated group.  During the year ended 30 June 2012, AGL received an unfavourable response from the Australian Taxation Office (ATO) to a request for  a private binding ruling relating to the tax treatment of the supply of unbilled energy to AGL’s mass market customers. AGL’s current tax  treatment is to pay income tax on energy when it is billed to customers. If the ATO view is correct, AGL would be required to pay income  tax on energy when it is supplied to customers rather than when it is billed and AGL would be required to recognise the tax as a current  tax liability rather than a deferred tax liability. AGL believes its current tax treatment is correct and has therefore lodged an objection to  the private binding ruling. Changes to the Petroleum Resource Rent Tax (PRRT) Assessment Act 1987 extend the operation of the PRRT to onshore oil and gas  projects from 1 July 2012. As the PRRT falls within the scope of AASB 112  Income Taxes , AGL is required to account for any associated  deferred tax assets or deferred tax liabilities as at 30 June 2012. AGL has recognised a deferred tax asset of $53.4 million representing  the difference between the PRRT starting base amount and the carrying value of the production permits to which the PRRT will apply.