<?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>117 - Disclosure - MAJOR CUSTOMERS AND CREDIT RISK</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>P10_01_2012To06_30_2013</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001242513</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_SegmentReportingAbstract</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>Segment Reporting [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_SegmentReportingDisclosureTextBlock</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="P10_01_2012To06_30_2013" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>              &lt;div style="clear:both; FONT-FAMILY:Times New Roman;FONT-SIZE: 10pt;MARGIN: 0pt 0px; FONT: 10pt Times New Roman, Times, Serif "&gt;  &lt;div style="clear:both; FONT-FAMILY:Times New Roman;FONT-SIZE: 10pt;TEXT-ALIGN: justify; MARGIN: 0pt 0px; FONT: 10pt Times New Roman, Times, Serif"&gt;  &lt;font style="FONT-FAMILY: Times New Roman, Times, Serif"&gt;&lt;strong&gt;  Note 12 - &lt;u&gt;MAJOR CUSTOMERS AND CREDIT  RISK&lt;/u&gt;&lt;/strong&gt;&lt;/font&gt;&lt;/div&gt;    &lt;div style="clear:both; FONT-FAMILY:Times New Roman;FONT-SIZE: 10pt"&gt;  &amp;#160;&lt;/div&gt;    &lt;div style="clear:both; FONT-FAMILY:Times New Roman;FONT-SIZE: 10pt;TEXT-ALIGN: justify; MARGIN: 0pt 0px; FONT: 10pt Times New Roman, Times, Serif"&gt;  &lt;font style="FONT-FAMILY: Times New Roman, Times, Serif"&gt;Four and  four customers accounted for more than &lt;font style=" FONT-SIZE: 10pt"&gt;&lt;font style=" FONT-SIZE: 10pt"&gt;5&lt;/font&gt;&lt;/font&gt;%  of accounts receivable at June 30, 2013 and September 30, 2012,  totaling &lt;font style=" FONT-SIZE: 10pt"&gt;62&lt;/font&gt;% and &lt;font style=" FONT-SIZE: 10pt"&gt;54&lt;/font&gt;% respectively. For the nine months  ended June 30, 2013 and 2012, one and one customer accounted for  greater than &lt;font style=" FONT-SIZE: 10pt"&gt;10&lt;/font&gt;% of total  sales amounts, totaling &lt;font style=" FONT-SIZE: 10pt"&gt;22&lt;/font&gt;%  and &lt;font style=" FONT-SIZE: 10pt"&gt;17&lt;/font&gt;% respectively. For the  three months ended June 30, 2013 and 2012, one and one customer  accounted for greater than &lt;font style=" FONT-SIZE: 10pt"&gt;  10&lt;/font&gt;% of total sales amounts, totaling &lt;font style=" FONT-SIZE: 10pt"&gt;23&lt;/font&gt;% and &lt;font style=" FONT-SIZE: 10pt"&gt;  17&lt;/font&gt;% respectively.&lt;/font&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 reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 1

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8380-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 32

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8933-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 10

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8538-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 26

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8844-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 29

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8864-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 34

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8981-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 35

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8984-108599



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

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 41

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e9038-108599



Reference 9: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 30

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8906-108599



Reference 10: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 42

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e9054-108599



Reference 11: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 31

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8924-108599



Reference 12: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 40

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e9031-108599



Reference 13: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 33

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8971-108599



Reference 14: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 280

 -SubTopic 10

 -Section 50

 -Paragraph 12

 -URI http://asc.fasb.org/extlink&amp;oid=6534315&amp;loc=d3e8595-108599



</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Segment Reporting Disclosure [Text Block]</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>MAJOR CUSTOMERS AND CREDIT RISK</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.cgii.com/role/MajorCustomersAndCreditRisk</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
