<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-02-09</periodOfReport>

    <issuer>
        <issuerCik>0001125259</issuerCik>
        <issuerName>CARNIVAL PLC</issuerName>
        <issuerTradingSymbol>CUK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001622005</rptOwnerCik>
            <rptOwnerName>NOYES DAVID MICHAEL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CARNIVAL CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>3655 N.W. 87TH AVENUE</rptOwnerStreet2>
            <rptOwnerCity>MIAMI</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33178</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>CEO - Carnival UK</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2016-02-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1522</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13472.332</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2016-02-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>843</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.79</value>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12629.332</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Grant of performance-based restricted stock units (&quot;Performance RSUs&quot;) granted on July 16, 2013 pursuant to the Carnival plc 2005 Employee Share Plan.  Each Performance RSU represents one share of Carnival plc ordinary shares.</footnote>
        <footnote id="F2">Reporting person was eligible to earn from 0-150% of his target amount of Performance RSUs to the extent that Carnival Corporation &amp; plc's annual earnings before interest and taxes (&quot;EBIT&quot;), as adjusted for certain fuel price changes and Emission Control Areas related fuel expenses, for each of the three fiscal years in the 2013-2015 performance cycle exceeded specified performance goals, as modified at the end of the three year performance cycle for Carnival Corporation &amp; plc's total shareholder return rank relative to peers.</footnote>
        <footnote id="F3">Includes shares from a settlement of dividend equivalents accumulated during the restricted period of a Performance RSU award originally granted in 2013, which has now vested.</footnote>
        <footnote id="F4">Represents a surrender of shares to satisfy the tax obligation on the vesting of the Performance RSUs.</footnote>
        <footnote id="F5">The transaction was conducted in British Pounds. The sale price of GBP29.83706 was converted into US$ at the February 9, 2016 conversion rate of GBP1 = USD1.4436. This transaction was executed in multiple trades. The price reported reflects the average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David M. Noyes</signatureName>
        <signatureDate>2016-02-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
