<?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>0013 - Disclosure - 8. Tax payables</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>From2013-01-01to2013-06-30</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000828878</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 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>GCIH_TaxPayablesAbstract</ElementName><ElementPrefix>GCIH_</ElementPrefix><IsBaseElement>false</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>Tax Payables</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>GCIH_TaxesPayableTextBlock</ElementName><ElementPrefix>GCIH_</ElementPrefix><IsBaseElement>false</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="From2013-01-01to2013-06-30" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 8pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;Tax payables consisted of the following:&lt;/p&gt;

&lt;p style="font: 8pt Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&amp;#160;&lt;/p&gt;

&lt;table cellspacing="0" cellpadding="0" style="font: 8pt Times New Roman, Times, Serif; width: 100%"&gt;
&lt;tr style="vertical-align: top"&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1.5pt solid; text-align: center"&gt;&lt;font style="font-size: 8pt"&gt;&lt;b&gt;June 30, 2013&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1.5pt solid; text-align: center"&gt;&lt;font style="font-size: 8pt"&gt;&lt;b&gt;December 31, 2012&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: top"&gt;
    &lt;td style="width: 81%"&gt;&lt;font style="font-size: 8pt"&gt;Income tax payable in Mainland China&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%"&gt;&lt;font style="font-size: 8pt"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 8%; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;1,465,514&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%"&gt;&lt;font style="font-size: 8pt"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 8%; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;1,230,221&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td&gt;&lt;font style="font-size: 8pt"&gt;Business tax&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;637,657&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;669,202&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td&gt;&lt;font style="font-size: 8pt"&gt;Land VAT payable&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;2,444,865&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;2,408,488&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td&gt;&lt;font style="font-size: 8pt"&gt;Other levies&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;-34,263&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;46,942&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td&gt;&lt;font style="font-size: 8pt"&gt;&lt;b&gt;Total&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double"&gt;&lt;font style="font-size: 8pt"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;4,513,773&lt;/font&gt;&lt;/td&gt;
    &lt;td&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double"&gt;&lt;font style="font-size: 8pt"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right"&gt;&lt;font style="font-size: 8pt"&gt;4,354,853&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
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