| | | | | | | | | | | | | | | | | | | | | |
<?xml version="1.0" encoding="windows-1252"?> |
<FilingSummary> |
| <Version> 3.24.0.1 </Version> |
| <ProcessingTime/> |
| <ReportFormat> html </ReportFormat> |
| <ContextCount> 1281 </ContextCount> |
| <ElementCount> 116 </ElementCount> |
| <EntityCount> 1 </EntityCount> |
| <FootnotesReported> false </FootnotesReported> |
| <SegmentCount> 29 </SegmentCount> |
| <ScenarioCount> 0 </ScenarioCount> |
| <TuplesReported> false </TuplesReported> |
| <UnitCount> 6 </UnitCount> |
| <MyReports> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R1.htm </HtmlFileName> |
| | | <LongName> 00090 - Document - Document and Entity Information </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DocumentDocumentAndEntityInformation </Role> |
| | | <ShortName> Document and Entity Information </ShortName> |
| | | <MenuCategory> Cover </MenuCategory> |
| | | <Position> 1 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R2.htm </HtmlFileName> |
| | | <LongName> 00100 - Statement - CONDENSED BALANCE SHEETS (Unaudited) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/StatementCondensedBalanceSheetsUnaudited </Role> |
| | | <ShortName> CONDENSED BALANCE SHEETS (Unaudited) </ShortName> |
| | | <MenuCategory> Statements </MenuCategory> |
| | | <Position> 2 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R3.htm </HtmlFileName> |
| | | <LongName> 00105 - Statement - CONDENSED BALANCE SHEETS (Parenthetical) (Unaudited) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/StatementCondensedBalanceSheetsParentheticalUnaudited </Role> |
| | | <ShortName> CONDENSED BALANCE SHEETS (Parenthetical) (Unaudited) </ShortName> |
| | | <MenuCategory> Statements </MenuCategory> |
| | | <Position> 3 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R4.htm </HtmlFileName> |
| | | <LongName> 00200 - Statement - CONDENSED STATEMENTS OF OPERATIONS (Unaudited) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/StatementCondensedStatementsOfOperationsUnaudited </Role> |
| | | <ShortName> CONDENSED STATEMENTS OF OPERATIONS (Unaudited) </ShortName> |
| | | <MenuCategory> Statements </MenuCategory> |
| | | <Position> 4 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R5.htm </HtmlFileName> |
| | | <LongName> 00300 - Statement - CONDENSED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (DEFICIT) (Unaudited) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/StatementCondensedStatementsOfChangesInPartnersCapitalDeficitUnaudited </Role> |
| | | <ShortName> CONDENSED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (DEFICIT) (Unaudited) </ShortName> |
| | | <MenuCategory> Statements </MenuCategory> |
| | | <Position> 5 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R6.htm </HtmlFileName> |
| | | <LongName> 00400 - Statement - CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/StatementCondensedStatementsOfCashFlowsUnaudited </Role> |
| | | <ShortName> CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) </ShortName> |
| | | <MenuCategory> Statements </MenuCategory> |
| | | <Position> 6 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R7.htm </HtmlFileName> |
| | | <LongName> 10101 - Disclosure - ORGANIZATION </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureOrganization </Role> |
| | | <ShortName> ORGANIZATION </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 7 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R8.htm </HtmlFileName> |
| | | <LongName> 10201 - Disclosure - ACCOUNTING AND FINANCIAL REPORTING POLICIES </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureAccountingAndFinancialReportingPolicies </Role> |
| | | <ShortName> ACCOUNTING AND FINANCIAL REPORTING POLICIES </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 8 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R9.htm </HtmlFileName> |
| | | <LongName> 10301 - Disclosure - RELATED PARTY TRANSACTIONS </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactions </Role> |
| | | <ShortName> RELATED PARTY TRANSACTIONS </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 9 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R10.htm </HtmlFileName> |
| | | <LongName> 10401 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnerships </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 10 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R11.htm </HtmlFileName> |
| | | <LongName> 10501 - Disclosure - TAXABLE LOSS </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureTaxableLoss </Role> |
| | | <ShortName> TAXABLE LOSS </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 11 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R12.htm </HtmlFileName> |
| | | <LongName> 10601 - Disclosure - INCOME TAXES </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureIncomeTaxes </Role> |
| | | <ShortName> INCOME TAXES </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 12 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R13.htm </HtmlFileName> |
| | | <LongName> 10701 - Disclosure - SUBSEQUENT EVENTS </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureSubsequentEvents </Role> |
| | | <ShortName> SUBSEQUENT EVENTS </ShortName> |
| | | <MenuCategory> Notes </MenuCategory> |
| | | <Position> 13 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R14.htm </HtmlFileName> |
| | | <LongName> 30103 - Disclosure - ORGANIZATION (Tables) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureOrganizationTables </Role> |
| | | <ShortName> ORGANIZATION (Tables) </ShortName> |
| | | <MenuCategory> Tables </MenuCategory> |
| | | <ParentRole> http://www.bostoncapital.com/role/DisclosureOrganization </ParentRole> |
| | | <Position> 14 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R15.htm </HtmlFileName> |
| | | <LongName> 30303 - Disclosure - RELATED PARTY TRANSACTIONS (Tables) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactionsTables </Role> |
| | | <ShortName> RELATED PARTY TRANSACTIONS (Tables) </ShortName> |
| | | <MenuCategory> Tables </MenuCategory> |
| | | <ParentRole> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactions </ParentRole> |
| | | <Position> 15 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R16.htm </HtmlFileName> |
| | | <LongName> 30403 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS (Tables) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsTables </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS (Tables) </ShortName> |
| | | <MenuCategory> Tables </MenuCategory> |
| | | <ParentRole> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnerships </ParentRole> |
| | | <Position> 16 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R17.htm </HtmlFileName> |
| | | <LongName> 40101 - Disclosure - ORGANIZATION - BACs sold and total equity raised by series (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureOrganizationBacsSoldAndTotalEquityRaisedBySeriesDetails </Role> |
| | | <ShortName> ORGANIZATION - BACs sold and total equity raised by series (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 17 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R18.htm </HtmlFileName> |
| | | <LongName> 40102 - Disclosure - ORGANIZATION - Additional Information (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureOrganizationAdditionalInformationDetails </Role> |
| | | <ShortName> ORGANIZATION - Additional Information (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 18 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R19.htm </HtmlFileName> |
| | | <LongName> 40301 - Disclosure - RELATED PARTY TRANSACTIONS - Fund management fees accrued (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactionsFundManagementFeesAccruedDetails </Role> |
| | | <ShortName> RELATED PARTY TRANSACTIONS - Fund management fees accrued (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 19 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R20.htm </HtmlFileName> |
| | | <LongName> 40302 - Disclosure - RELATED PARTY TRANSACTIONS - Fund management fees paid (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactionsFundManagementFeesPaidDetails </Role> |
| | | <ShortName> RELATED PARTY TRANSACTIONS - Fund management fees paid (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 20 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R21.htm </HtmlFileName> |
| | | <LongName> 40303 - Disclosure - RELATED PARTY TRANSACTIONS - Additional Information (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureRelatedPartyTransactionsAdditionalInformationDetails </Role> |
| | | <ShortName> RELATED PARTY TRANSACTIONS - Additional Information (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 21 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R22.htm </HtmlFileName> |
| | | <LongName> 40401 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS - Operating Partnerships within the Fund (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsOperatingPartnershipsWithinFundDetails </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS - Operating Partnerships within the Fund (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 22 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R23.htm </HtmlFileName> |
| | | <LongName> 40402 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS - Contributions payable (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsContributionsPayableDetails </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS - Contributions payable (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 23 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R24.htm </HtmlFileName> |
| | | <LongName> 40403 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS - Dispositions by series (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsDispositionsBySeriesDetails </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS - Dispositions by series (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 24 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R25.htm </HtmlFileName> |
| | | <LongName> 40404 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS - Current financial results available for the Operating Partnerships (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsCurrentFinancialResultsAvailableForOperatingPartnershipsDetails </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS - Current financial results available for the Operating Partnerships (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 25 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R26.htm </HtmlFileName> |
| | | <LongName> 40405 - Disclosure - INVESTMENTS IN OPERATING PARTNERSHIPS - Additional Information (Details) </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://www.bostoncapital.com/role/DisclosureInvestmentsInOperatingPartnershipsAdditionalInformationDetails </Role> |
| | | <ShortName> INVESTMENTS IN OPERATING PARTNERSHIPS - Additional Information (Details) </ShortName> |
| | | <MenuCategory> Details </MenuCategory> |
| | | <Position> 26 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R27.htm </HtmlFileName> |
| | | <LongName> 995410 - Disclosure - Pay vs Performance Disclosure </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://xbrl.sec.gov/ecd/role/PvpDisclosure </Role> |
| | | <ShortName> Pay vs Performance Disclosure </ShortName> |
| | | <MenuCategory> Uncategorized </MenuCategory> |
| | | <Position> 27 </Position> |
| | | </Report> |
| | <Report instance="bctciv-20231231x10q.htm"> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <HtmlFileName> R28.htm </HtmlFileName> |
| | | <LongName> 995445 - Disclosure - Insider Trading Arrangements </LongName> |
| | | <ReportType> Sheet </ReportType> |
| | | <Role> http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements </Role> |
| | | <ShortName> Insider Trading Arrangements </ShortName> |
| | | <MenuCategory> Cover </MenuCategory> |
| | | <Position> 28 </Position> |
| | | </Report> |
| | <Report> |
| | | <IsDefault> false </IsDefault> |
| | | <HasEmbeddedReports> false </HasEmbeddedReports> |
| | | <LongName> All Reports </LongName> |
| | | <ReportType> Book </ReportType> |
| | | <ShortName> All Reports </ShortName> |
| | | </Report> |
| | </MyReports> |
| <InputFiles> |
| | <File> bctciv-20231231.xsd </File> |
| | <File> bctciv-20231231_cal.xml </File> |
| | <File> bctciv-20231231_def.xml </File> |
| | <File> bctciv-20231231_lab.xml </File> |
| | <File> bctciv-20231231_pre.xml </File> |
| | <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="bctciv-20231231x10q.htm"> bctciv-20231231x10q.htm </File> |
| | </InputFiles> |
| <SupplementalFiles/> |
| <BaseTaxonomies> |
| | <BaseTaxonomy items="4295"> http://fasb.org/us-gaap/2023 </BaseTaxonomy> |
| | <BaseTaxonomy items="30"> http://xbrl.sec.gov/dei/2023 </BaseTaxonomy> |
| | <BaseTaxonomy items="4"> http://xbrl.sec.gov/ecd/2023 </BaseTaxonomy> |
| | </BaseTaxonomies> |
| <HasPresentationLinkbase> true </HasPresentationLinkbase> |
| <HasCalculationLinkbase> true </HasCalculationLinkbase> |
| </FilingSummary> |