Tax Reporting Package

Beginning in early March, MPLX LP (“MPLX”) will begin mailing 2015 tax packages to unitholders. The 2015 Schedule K-1 information will also be available online to unitholders in early March using the websites below. You can access the websites and register to be notified when the tax packages are available.

Please note that as a result of the merger of MPLX with MarkWest Energy Partners, L.P. (“MWE”), unitholders that held MPLX units both before and after the Dec. 4, 2015 merger will receive two Schedule K-1s for the 2015 reporting year. You can access the tax reporting websites by clicking the below links.

To access the tax reporting website for the year ended Dec. 3, 2015 tax packages, click the below link:

MPLX Tax Reporting Package - Year Ended Dec 3, 2015

To access the tax reporting website for the year ended Dec. 31, 2015 tax packages, click the below link:

MPLX Tax Reporting Package - Year Ended Dec. 31, 2015

Former MWE Unitholders

Former MWE unitholders receiving a 2015 Schedule K-1 can access the tax reporting website at the below link:

Combined MWE/MPLX Tax Reporting Package - Year Ended Dec. 31, 2015

Important Tax Information for MWE Unitholders on record at close of trading on Dec. 3, 2015

The below document contains general tax information that may be helpful for former MWE unitholders who received cash consideration and MPLX units in exchange for their MWE units.

Tax information for MarkWest Energy Partners, L.P. unitholders.