<?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>103 - Disclosure - INVESTMENT AT EQUITY</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-2012-10-01-to-2013-06-30.1650.0.0.0.0.0.0.0</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000314712</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2012-10-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="9 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_EquityMethodInvestmentsAndJointVenturesAbstract</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>INVESTMENT AT EQUITY [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_EquityMethodInvestmentsDisclosureTextBlock</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>verboseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="from-2012-10-01-to-2013-06-30.1650.0.0.0.0.0.0.0" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;&lt;div&gt; &lt;div&gt;&lt;!--StartFragment--&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &lt;strong&gt;NOTE 3 - INVESTMENT AT EQUITY&lt;/strong&gt;&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px; TEXT-INDENT: 0.5in"&gt; &amp;nbsp;&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; Until May 31, 2013, the Company was a partner in the United Arab Emirates "UAE" joint venture, Boomerang Systems Middle East, LLC.&amp;nbsp;&amp;nbsp; Boomerang Systems Middle East, LLC is owned by Boomerang Systems USA Corp. (49%), a subsidiary of Boomerang Systems, Inc., and Tawreed Companies Representation (51%), a UAE company.&amp;nbsp;&amp;nbsp;The equity method is used to calculate the current amount of this investment.&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px; TEXT-INDENT: 0.5in"&gt; &amp;nbsp;&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; During the nine months ended June 30, 2013, the Company made additional investments in the UAE joint venture totaling $15,000.&amp;nbsp;&amp;nbsp;The joint venture was terminated on May 31, 2013. Boomerang recorded a loss of the entire investment during the nine months ended June 30, 2013. Based on the equity method, the 49% loss we recognized on this investment for the nine months ended June 30, 2013 was $157,899.&amp;nbsp;&amp;nbsp;The carrying value on this investment was $0 at June 30, 2013.&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &amp;nbsp;&lt;/p&gt; &lt;table style="BORDER-COLLAPSE: collapse; FONT: 10pt Times New Roman, Times, Serif; WIDTH: 40%" cellspacing="0" cellpadding="0"&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: rgb(204,255,204)"&gt; &lt;td style="WIDTH: 80%"&gt;Balance as of September 30, 2012&lt;/td&gt; &lt;td style="WIDTH: 1%"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: left; WIDTH: 1%"&gt;$&lt;/td&gt; &lt;td style="TEXT-ALIGN: right; WIDTH: 17%"&gt;142,899&lt;/td&gt; &lt;td style="TEXT-ALIGN: left; WIDTH: 1%"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: white"&gt; &lt;td style="TEXT-ALIGN: left"&gt;Additional investment&lt;/td&gt; &lt;td&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: right"&gt;15,000&lt;/td&gt; &lt;td style="TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: rgb(204,255,204)"&gt; &lt;td style="PADDING-BOTTOM: 1pt; TEXT-ALIGN: left"&gt;Loss on investment (49%)&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 1pt"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 1pt solid; TEXT-ALIGN: left"&gt; &amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 1pt solid; TEXT-ALIGN: right"&gt; (157,899&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 1pt; TEXT-ALIGN: left"&gt;)&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: white"&gt; &lt;td style="PADDING-BOTTOM: 2.5pt"&gt;Balance as of June 30, 2013&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 2.5pt"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 2.5pt double; TEXT-ALIGN: left"&gt; $&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 2.5pt double; TEXT-ALIGN: right"&gt; -&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 2.5pt; TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &amp;nbsp;&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; On February 15, 2012, Boomerang MP Holdings, Inc., a wholly owned subsidiary of the Company, was formed with the purpose of entering into a mechanical parking joint venture. On February 16, 2012, Boomerang MP Holdings, Inc., formed a joint venture with Stokes Industries-USA, LLC ("Stokes"). The joint venture, Boomerang-Stokes Mechanical Parking LLC, is owned 50% by Boomerang MP Holdings, Inc. and 50% by Stokes. Boomerang MP Holdings, Inc., is committed to providing a minimum of $250,000 of capital to fund the initial operations and marketing efforts during the initial two year period of the joint venture. Boomerang MP Holdings, Inc., shall also license the name "Boomerang" to the joint venture for use in North America on a royalty free, non-exclusive basis.&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &amp;nbsp;&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; During the nine months ended June 30, 2013, the Company made additional investments totaling $159,236 in the joint venture. The joint venture was terminated on April 21, 2013. Boomerang recorded a loss of the entire investment during the nine months ended June 30, 2013. Based on the equity method, the loss we recognized on this investment for the nine months ended June 30, 2013 was $246,532. The carrying value on this investment was $0 at June 30, 2013.&lt;/p&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &amp;nbsp;&lt;/p&gt; &lt;table style="BORDER-COLLAPSE: collapse; FONT: 10pt Times New Roman, Times, Serif; WIDTH: 40%" cellspacing="0" cellpadding="0"&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: rgb(204,255,204)"&gt; &lt;td style="WIDTH: 80%"&gt;Balance as of September 30, 2012&lt;/td&gt; &lt;td style="WIDTH: 1%"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: left; WIDTH: 1%"&gt;$&lt;/td&gt; &lt;td style="TEXT-ALIGN: right; WIDTH: 17%"&gt;87,296&lt;/td&gt; &lt;td style="TEXT-ALIGN: left; WIDTH: 1%"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: white"&gt; &lt;td style="TEXT-ALIGN: left"&gt;Additional investment&lt;/td&gt; &lt;td&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="TEXT-ALIGN: right"&gt;159,236&lt;/td&gt; &lt;td style="TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: rgb(204,255,204)"&gt; &lt;td style="PADDING-BOTTOM: 1pt; TEXT-ALIGN: left"&gt;Loss on investment (50%)&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 1pt"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 1pt solid; TEXT-ALIGN: left"&gt; &amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 1pt solid; TEXT-ALIGN: right"&gt; (246,532&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 1pt; TEXT-ALIGN: left"&gt;)&lt;/td&gt; &lt;/tr&gt; &lt;tr style="VERTICAL-ALIGN: bottom; BACKGROUND-COLOR: white"&gt; &lt;td style="PADDING-BOTTOM: 2.5pt"&gt;Balance as of June 30, 2013&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 2.5pt"&gt;&amp;nbsp;&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 2.5pt double; TEXT-ALIGN: left"&gt; $&lt;/td&gt; &lt;td style="BORDER-BOTTOM: black 2.5pt double; TEXT-ALIGN: right"&gt; -&lt;/td&gt; &lt;td style="PADDING-BOTTOM: 2.5pt; TEXT-ALIGN: left"&gt;&amp;nbsp;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;p style="FONT: 10pt Times New Roman, Times, Serif; MARGIN: 0pt 0px"&gt; &amp;nbsp;&lt;/p&gt; &lt;!--EndFragment--&gt;&lt;/div&gt; &lt;/div&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 equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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