<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>101300 - Disclosure - Income Tax Provision</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>FROM_Apr01_2013_TO_Jun30_2013</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000834071</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-04-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="3 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_IncomeTaxDisclosureAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Income Tax Provision [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_IncomeTaxDisclosureTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="FROM_Apr01_2013_TO_Jun30_2013" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;font-weight:bold;text-decoration:underline;margin-left:0px;"&gt;Note 13 &amp;#8211; Income Taxes &lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;margin-left:0px;"&gt;Our effective tax rate &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;was 37&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; percent for&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; both&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; the three months ended&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; June 30, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; and&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;June 30, 2012&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.  Our provision for income taxes for the first quarter&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; of fiscal 2014&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; was $53&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; million compared to $279&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; million for the same period in fiscal 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.&amp;#160; The decrease in the provision is consistent with the decrease in our income before tax for the first &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;three&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; months of fiscal 2014&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; compared to the same period in fiscal 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;font-weight:bold;font-style:italic;margin-left:0px;"&gt;Tax-related Contingencies&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;margin-left:0px;"&gt;As of &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;June 30, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;, &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;we remain under IRS examination for the fiscal years ended March 31, 201&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;2 &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;and &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;March 31, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;, as well as for the current fiscal year&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;margin-left:0px;"&gt;We periodically review our uncertain tax positions.  Our assessment is based on many factors including the ongoing IRS audits.  For the quarter ended June 30, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;, our assessment did not result in a material change in unrecognized tax benefits.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;margin-left:0px;"&gt;Our deferred tax assets&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;were $1.2 billion&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; at June 30, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;and&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;March 31, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;, and were primarily due to the deferred deduction of allowance for credit losses and cumulative federal tax loss &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;carryforwards&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; that expire in varying amounts through fiscal 2033&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.  The total deferred tax liability at June 30, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;, net of these deferred tax assets, was $6.3 billion compared with $6.2 billion at March 31, 2013&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.  Realization with respect to the federal tax loss &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;carryforwards&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt; is dependent on generating sufficient income prior to expiration of the loss &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;carryforwards&lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:11pt;"&gt;.  Although realization is not assured, management believes it is more likely than not that the deferred tax assets will be realized.  The amount of the deferred tax assets considered realizable could be reduced if management's estimates change.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 740

 -SubTopic 10

 -Section 50

 -Paragraph 15

 -URI http://asc.fasb.org/extlink&amp;oid=6907707&amp;loc=d3e32718-109319



Reference 2: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 235

 -SubTopic 10

 -Section S99

 -Paragraph 1

 -Subparagraph (SX 210.4-08.(h))

 -URI http://asc.fasb.org/extlink&amp;oid=6881521&amp;loc=d3e23780-122690



Reference 3: http://www.xbrl.org/2003/role/presentationRef

 -Publisher SEC

 -Name Regulation S-X (SX)

 -Number 210

 -Section 08

 -Paragraph h

 -Article 4



Reference 4: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 740

 -SubTopic 10

 -Section 50

 -Paragraph 9

 -URI http://asc.fasb.org/extlink&amp;oid=6907707&amp;loc=d3e32639-109319



Reference 5: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 740

 -SubTopic 10

 -Section 50

 -Paragraph 2

 -URI http://asc.fasb.org/extlink&amp;oid=6907707&amp;loc=d3e32537-109319



Reference 6: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 740

 -SubTopic 10

 -Section 50

 -Paragraph 3

 -URI http://asc.fasb.org/extlink&amp;oid=6907707&amp;loc=d3e32559-109319



Reference 7: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Statement of Financial Accounting Standard (FAS)

 -Number 109

 -Paragraph 136, 172

 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 8: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Statement of Financial Accounting Standard (FAS)

 -Number 109

 -Paragraph 43, 44, 45, 46, 47, 48, 49

 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Income Tax Provision</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>Income Tax Provision</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://www.toyotafinancial.com/role/IncomeTaxProvision</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
