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Risk/Return:

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Supplement [Text Block]

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SEI INSTITUTIONAL MANAGED TRUST

Tax-Managed Large Cap Fund
(the "Fund")

Supplement dated April 1, 2014
to the Class A Shares Prospectus (the "Prospectus") dated January 31, 2014

This Supplement provides new and additional information beyond that contained in the Class A Shares Prospectus and should be read in conjunction with such Prospectus.

Risk/Return [Heading]

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SIMT TAX-MANAGED LARGE CAP FUND

Bar Chart and Performance Table [Heading]

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Change in Performance Information for the Tax-Managed Large Cap Fund

Performance Narrative [Text Block]

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In the table under the heading "Average Annual Total Returns (for the periods ended December 31, 2013)," in the "Performance Information" section of the Fund Summary for the Tax-Managed Large Cap Fund, the row related to "Return After Taxes on Distributions" is hereby deleted and replaced with the following:

Performance Table Closing [Text Block]

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There are no other changes in the performance information of the Tax-Managed Large Cap Fund.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

SIMT TAX-MANAGED LARGE CAP FUND - CLASS A

Risk/Return:

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Average Annual Returns, Inception Date

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Mar. 05, 1998

SIMT TAX-MANAGED LARGE CAP FUND - CLASS A | After Taxes on Distributions

Risk/Return:

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Label

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Return After Taxes on Distributions

Average Annual Returns, 1 Year

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34.49%

Average Annual Returns, 5 Years

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18.01%

Average Annual Returns, 10 Years

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7.05%

Average Annual Returns, Since Inception

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4.75%