| | | | | | | | | | | | | | | | | | | | | | |
| <?xml version="1.0" encoding="windows-1252"?> |
| <ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2022-10-03 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0000277948 </issuerCik> |
| | <issuerName> CSX CORP </issuerName> |
| | <issuerTradingSymbol> CSX </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001790747 </rptOwnerCik> |
| | | <rptOwnerName> Boychuk Jamie J. </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> 500 WATER STREET </rptOwnerStreet1> |
| | | <rptOwnerStreet2></rptOwnerStreet2> |
| | | <rptOwnerCity> JACKSONVILLE </rptOwnerCity> |
| | | <rptOwnerState> FL </rptOwnerState> |
| | | <rptOwnerZipCode> 32202 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 1 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle> EVP - Operations </officerTitle> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <derivativeTable> |
| | <derivativeTransaction> |
| | | <securityTitle> |
| <value> Phantom Stock </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <footnoteId id="F1"/> |
| </conversionOrExercisePrice> |
| | | <transactionDate> |
| <value> 2022-10-03 </value> |
| </transactionDate> |
| | | <deemedExecutionDate></deemedExecutionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> A </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| </transactionCoding> |
| | | <transactionTimeliness> |
| <value></value> |
| </transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 121 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 27.42 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> A </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <exerciseDate> |
| <footnoteId id="F1"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <footnoteId id="F1"/> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 121 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 2144 </value> |
| <footnoteId id="F2"/> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> I </value> |
| </directOrIndirectOwnership> |
| <natureOfOwnership> |
| <value> CSX Executive Deferred Compensation Plan </value> |
| <footnoteId id="F3"/> |
| </natureOfOwnership> |
| </ownershipNature> |
| | | </derivativeTransaction> |
| | </derivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Each unit of phantom stock is the economic equivalent of one share of Company common stock. Units of phantom stock become payable, in cash, consistent with the Reporting Person's distribution election made at the time of deferral. </footnote> |
| | <footnote id="F2"> Includes 6.335 units of phantom stock acquired in connection with the payment of a dividend on September 15, 2022 at $30.17 per share. </footnote> |
| | <footnote id="F3"> By Trustee, CSX Corporation Executive Deferred Compensation Plan. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> /s/ Michael S. Burns, Attorney-in-Fact </signatureName> |
| | <signatureDate> 2022-10-05 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |
