72 Consolidated  Notes to the  Financial  Statements Note 1 – Summary of significant accounting policies  (continued) (ad) Revenue recognition (ae) Net fi nancing costs Current tax Deferred tax (af) Goods and services tax Current and deferred tax for the period Tax consolidation (ag) Income tax The tax currently payable is based on taxable profit for the year.  Taxable profit differs from profit as reported in the consolidated  income statement because of items of income or expense that are  taxable or deductible in other years and items that are never  taxable or deductible. The consolidated entity’s liability for current  tax is calculated using tax rates that have been enacted or  substantively enacted by the end of the reporting period. Revenue is recognised and measured at the fair value of the  consideration received or receivable to the extent it is probable  that the economic benefits will flow to the consolidated entity and  the revenue can be reliably measured. Revenue from gas and electricity services supplied is recognised  once the gas and electricity has been delivered to the customer and  is measured through a regular review of usage meters. Customers  are billed on a periodic and regular basis. At the end of each  reporting period, gas and electricity revenue includes an accrual for  energy delivered to customers but not yet billed (unbilled revenue). Deferred tax is recognised on temporary differences between the  carrying amounts of assets and liabilities in the financial statements  and the corresponding tax bases used in the computation of  taxable profit. Deferred tax liabilities are generally recognised for all  taxable temporary differences. Deferred tax assets are generally  recognised for all deductible temporary differences to the extent  that it is probable that taxable profits will be available against which  those deductible temporary differences can be utilised. Such  deferred tax assets and liabilities are not recognised if the  temporary difference arises from goodwill or from the initial  recognition (other than in a business combination) of other assets  and liabilities in a transaction that affects neither the taxable profit  nor the accounting profit. Revenue from the provision of services, including revenue from  construction contracts, represents consideration received or  receivable determined, where appropriate, in accordance with the  percentage of completion method, with the stage of completion of  each contract determined by reference to the proportion that  contract costs for work performed to date bears to the estimated  total contract costs. Revenue from the sale of crude oil is recognised after each  shipment is loaded and title passes to the customer. Dividend income is recognised when the consolidated entity’s right  to receive the payment is established. The carrying amount of deferred tax assets is reviewed at the end  of each reporting period and reduced to the extent that it is no  longer probable that sufficient taxable profits will be available to  allow all or part of the asset to be recovered. Interest income is recognised as it accrues in profit or loss, using  the effective interest method. Finance costs directly attributable to the acquisition, construction  or production of qualifying assets, which are assets that necessarily  take a substantial period of time to get ready for their intended use  or sale, are added to the cost of those assets, until such time as the  assets are substantially ready for their intended use or sale. All other finance costs are recognised in profit or loss in the period  in which they are incurred. Finance costs comprise interest expense  on borrowings calculated using the effective interest method,  amortisation of borrowing costs relating to long-term financing  facilities, unwinding of the discount on provisions and gains and  losses on certain hedging instruments that are recognised in profit  or loss. Deferred tax assets and liabilities are measured at the tax rates that  are expected to apply in the period in which the liability is settled or  the asset realised, based on tax rates (and tax laws) that have been  enacted or substantively enacted by the end of the reporting  period. The measurement of deferred tax liabilities and assets  reflects the tax consequences that would follow from the manner  in which the consolidated entity expects, at the end of the  reporting period, to recover or settle the carrying amount of its  assets and liabilities. Deferred tax assets and liabilities are offset when there is a legally  enforceable right to set off current tax assets against current tax  liabilities and when they relate to income taxes levied by the same  taxation authority and the consolidated entity intends to settle its  current tax assets and liabilities on a net basis. Current and deferred tax are recognised as an expense or income in  profit or loss, except when they relate to items that are recognised  outside profit or loss (whether in other comprehensive income or  directly in equity), in which case the tax is also recognised outside  profit or loss, or where they arise from the initial accounting for a  business combination. In the case of a business combination, the tax  effect is included in the accounting for the business combination. Revenue, expenses and assets are recognised net of the amount of  goods and services tax (GST), except: 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. Tax expense/income, deferred tax liabilities and deferred tax assets  arising from temporary differences of the members of the  tax-consolidated group are recognised in the separate financial  statements of the members of the tax-consolidated group using  the ‘stand alone taxpayer’ approach by reference to the carrying  amounts in the separate financial statements of each entity and the  Income tax expense represents the sum of the tax currently  payable and deferred tax. Cash flows are included in the statement of cash flows on a gross  basis. The GST component of cash flows arising from investing and  financing activities which is recoverable from, or payable to, the  taxation authority is classified within operating cash flows. The net amount of GST recoverable from, or payable to, the  taxation authority is included as part of receivables or payables in  the statement of financial position. – where the amount of GST incurred is not recoverable from the  taxation authority, it is recognised as part of the cost of  acquisition of an asset or as part of an item of expense; or – for receivables and payables which are recognised inclusive  of GST.