6. Taxation This note explains how our Group tax charge arises. The deferred tax section of the note also provides information on our expected future tax charges and sets out the tax assets held across the Group together with our view on whether or not we expect to be able to make use of these in the future. Accounting policies Income tax expense represents the sum of the current and deferred taxes. Current tax payable or recoverable is based on taxable profit for the year. Taxable profit differs from profit as reported in the income statement because some items of income or expense are taxable or deductible in different years or may never be taxable or deductible. The Group’s liability for current tax is calculated using tax rates and laws that have been enacted or substantively enacted by the reporting period date. The Group recognises provisions for uncertain tax positions when the Group has a present obligation as a result of a past event and management judge that it is probable that there will be a future outflow of economic benefits from the Group to settle the obligation. Uncertain tax positions are assessed and measured on an issue by issue basis within the jurisdictions that we operate using management’s estimate of the most likely outcome. The Group recognises interest on late paid taxes as part of financing costs, and any penalties, if applicable, as part of the income tax expense. Deferred tax is the tax expected to be payable or recoverable in the future arising from 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. It is accounted for using the statement of financial position liability method. Deferred tax liabilities are generally recognised for all taxable temporary differences and deferred tax assets are recognised to the extent that it is probable that temporary differences or taxable profits will be available against which deductible temporary differences can be utilised. Such assets and liabilities are not recognised if the temporary difference arises from the initial recognition (other than in a business combination) of assets and liabilities in a transaction that affects neither the taxable profit nor the accounting profit. Deferred tax liabilities are not recognised to the extent they arise from the initial recognition of non-tax deductible goodwill. Deferred tax liabilities are recognised for taxable temporary differences arising on investments in subsidiaries and associates, and interests in joint arrangements, except where the Group is able to control the reversal of the temporary difference and it is probable that the temporary difference will not reverse in the foreseeable future The carrying amount of deferred tax assets is reviewed at each reporting period date and adjusted to reflect changes in the Group’s assessment that sufficient taxable profits will be available to allow all or part of the asset to be recovered. Deferred tax is calculated at the tax rates that are expected to apply in the period when the liability is settled or the asset realised, based on tax rates that have been enacted or substantively enacted by the reporting period date. 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 either relate to income taxes levied by the same taxation authority on either the same taxable entity or on different taxable entities which intend to settle the current tax assets and liabilities on a net basis Tax is charged or credited to the income statement, except when it relates to items charged or credited to other comprehensive income or directly to equity, in which case the tax is recognised in other comprehensive income or in equity Note: 1 The income statement tax charge includes tax relief on capitalised interest UK operating profits are more than offset by statutory allowances for capital investment in the UK network and systems plus ongoing interest costs including those arising from the €10.3 billion of spectrum payments to the UK government in 2000 and 2013. <table> <tbody> <tr><td>Income tax expense</td><td></td><td></td><td></td></tr> <tr><td></td><td>2019</td><td>2018</td><td>2017</td></tr> <tr><td></td><td>€m</td><td>€m</td><td>€m</td></tr> <tr><td>United Kingdom corporation tax expense/(credit):</td><td></td><td></td><td></td></tr> <tr><td>Current year1</td><td>21</td><td>70</td><td>27</td></tr> <tr><td>Adjustments in respect of prior years</td><td>(9)</td><td>(5)</td><td>(3)</td></tr> <tr><td></td><td>12</td><td>65</td><td>24</td></tr> <tr><td>Overseas current tax expense/(credit):</td><td></td><td></td><td></td></tr> <tr><td>Current year</td><td>1,098</td><td>1,055</td><td>961</td></tr> <tr><td>Adjustments in respect of prior years</td><td>(48)</td><td>(102)</td><td>(35)</td></tr> <tr><td></td><td>1,050</td><td>953</td><td>926</td></tr> <tr><td>Total current tax expense</td><td>1,062</td><td>1,018</td><td>950</td></tr> <tr><td>Deferred tax on origination and reversal of temporary differences:</td><td></td><td></td><td></td></tr> <tr><td>United Kingdom deferred tax</td><td>(232)</td><td>39</td><td>(16)</td></tr> <tr><td>Overseas deferred tax</td><td>666</td><td>(1,936)</td><td>3,830</td></tr> <tr><td>Total deferred tax expense/(credit)</td><td>434</td><td>(1,897)</td><td>3,814</td></tr> <tr><td>Total income tax expense/(credit)</td><td>1,496</td><td>(879)</td><td>4,764</td></tr> </tbody> </table>

Question: What would be the average total current tax expense for 2017 and 2018 if 2017 total current tax expense was 800 €m?
Answer: 909

Question: What would be the average total current tax expense for 2018 and 2019 if 2018 total current tax expense was 1,200 €m?
Answer: 1131

Question: What would be the change in the average total current tax expense between 2017-2018, and 2018-2019 if 2017 total current tax expense was 900 €m?
Answer: 81